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MANUAL 



Military Field Engineering 

FOR THE USE OF 

OFFICERS AND TROOPS OF THE LINE. 

PREPARED AT THE 

UNITED STATES INFANTRY AND CAVALRY SCHOOL 

BY THE 

Department of Engineering, 

Capt. Wm. D. Beach, 3d Cavalry, Instructor. 



FIFTH EDITION 

«v:v*.sisc by 

' ■ J • ' ~ < . t , v . y 

Major Wm. D. Beach, 10th Cavalry, 

, . Member of (he 5 War Qolle^e Board. 
_ / Capt. E.> A. Root„ I0t;i Infantry. 
Capt. T. H. Slavens, Quartermaster, U. S. A. 



The Hddson-Kimbirly Publishing Co., 
Kansas City, Mo. 



LONDON: 
W. H. A^LEN & CO. (Limited), 

13 Waterloo Place, S. W. 
Publishers to the India Office. 







\V 






\ 



Entered according to the Act of Congress in the year 1897, by the 

hudson*klmberly publishing co., in the office of the 

Librarian of Congress, at Washington. 



Copyrighted 1902, by the 

hudson-klmberly publishing company, 

Kansas City. U. S. A. 



» •" • •• • 



1 • • . * 

• ;• • « 

1 . ' * , ' 



PREFACE. 

The necessity existing at the Infantry and Cavalry School 
for a text-book on Field Engineering, including the various 
military expedients recognized in our service, is deemed suffi- 
cient reason for the following pages. 

Most of the subjects treated of in this volume may be found 
in various military works published in our country during the 
past twenty-five years, but the fact remains that no one book 
has covered the required ground, nor has their revision been of 
very recent date; while, at the same time, the new field gun and 
small calibre rifle have necessarily modified previously exist- 
ing profiles of Field Works and Shelter Trenches. 

Access has been had to corresponding publications of the 
Germans, French, English and Austrians, as well as to our 
own Official Rebellion Records and many other available 
sources, native and foreign. 

It has been the endeavor to limit the scope of this work to 
subjects considered indispensable as a part of a line officer's 
education. 

The following Assistant Instructors in the Department of 
Engineering — viz.: 1st Lieut. E. A. Root, 19th Infantry; 1st 
Lieut. W. C. Wren, 17th Infantry, and 1st Lieut. T. H. Slavens, 
6th Cavalry, have been associated with the undersigned in the 
preparation of this volume. 

WM. D. BEACH, 
Captain, 3d Cavalry. 
U. S. Infantry and Cavalry School, 

Fort Leavenworth, Kansas, July, 1894. 



Headquarters of the Army, Adjutant-General's Office, 

Washington, March 25, 1895. 
Circular No. 4. 

With the approval of the Secretary of War, the special study 
of the books, pamphlets, orders, etc., hereinafter named, by 
officers of the army subject to examinations for promotion, is 

recommended: 

* * * * * * * * 

Manual of Field Engineering— Captain W. D. Beach, 3rd 

Cavalry. 

****** * * 

By command of Lieutenant-General Schofield. 

[Signed] GEO. D. RUGGLE& 
Adjutant-General. 



PREFACE TO FIFTH EDITION. 

A fifth edition of this manual having been called for, the re- 
visers have made certain alterations and additions which seem 
to them warranted by experiences which have fallen to their lot 
during the Spanish-American War and Philippine insurrection. 

The peculiar difficulties confronting a rapidly advancing army 
are such as to render familiarity with various military expedi- 
ents only a degree less important than an intimate acquaintance 
with one's weapon. The efficiency of a command may be para- 
lyzed by the lack of a practicable road or by reason of a broken 
bridge as effectually as by tactical blunders or failure to 
reconnoiter. 

Hasty intrenchments are more than ever important, and there 
seems little reason to doubt, judging from our experience before 
El Caney and at San Juan Hill, that odds of ten to one will here- 
after be necessary in order to successfully assault trenches de- 
fended by good infantry armed with a magazine rifle. This de- 
duction was originally made by Colonel A. L. Wagner, A. A.-G., in 
a report on El Caney, andr is borne out by a critical study of the 
fight at San Juan Hill and various actions during the Boer War 
in South Africa. 

Recent experiences but render more certain the assertion that 
the assailant will usually find it necessary to intrench, the de- 
fender always. 

Upon the line officer in the future as in the past will devolve 
the responsibility of tracing and directing the construction of 
shelter trenches as well as making intelligent use of expedients 
in bridging, rafting, road-building or camping. 

As modern civilization tends to diminish the number of men 
skilled in handicraft, so much the more important does it become 
that all officers should require greater familiarity with what 
are ordinarily termed "military expedients." Results may be 
reached in many ways, but their attainment with economy of life 
and treasure marks a soldier skilled in his art, a leader worthy 
the best traditions of the military service. 

W. D. B. 

Fort Leavenworth, Kansas, August, 1902. 



List of Books Consulted in the Preparation of this Work. 

Aide Memoire, R. E Vols. 1-2, 

A Move for Better Roads L. A. Haupt. 

Appleton's Cyclopaedia of Applied Mechanics, Vols. z-2. 

Civil Engineering. Wheeler. 

Cours de Fortification Passagere De Guise. 

Ecole de Fortification de Campagne French. 

Elements of Field Fortification Wheeler. 

Engineering News. Magazine. 

Engineer's Pocket-Book. . . Trautwine. 

Field Fortification. . . . . . Turner. 

Field Fortification Hutchinson. 

Field Works Brackenbury. 

Field Works Used in War. (Translation 

from the German) Wilson. 

Good Roads Magazine. 

Gun Powder and High Explosives Walke. 

International Cyclopaedia Dodd, Mead & Co. 

Journal of the Military Service Institution 

of the U.S. 
Journal of the U. S. Cavalry Association. 

Manual for Engineer Troops Duane. 

Manual of Military Engineering Ernst. 

Manual for Railway Engineers G. L. Vose. 

Manuel de Fortification de Campagne. . . . Brialmont. 
Manuel des Travaux de Fortification de 

Campagne, par un Capitaine d'Infanterie. 

Manuel de P'ortification Plessix and Legrand. 

xVlanual of Heavy Artillery Jidball. 

Military Bridges Haupt. 

Military Bridges Chester. 

Military Engineering, Instruction in Chatham Course 

Military Land Mines Mercur. 

Military Transport Furse. 

Modern High Explosives Eissler. 

Notes on Military Hygiene A. A. Woodhull. 

Official Records of the Rebellion, U. S . . . . War Department. 

Organization and Tactics Wagner. 

Pionier Taschenbuch, Berlin, 1893 Official. 

Report of Chief Signal Officer, U. S., 1893. . War Department. 

Roads and Railroads Chester. 

Roads and Railroads Gillespie* 

Roads, Streets, and Pavements Gillmore. 

Temporary Fortification e Chester. 

The American Railway Scribner. 

V. S. Bridge Equipage and Drill . . , . War Department* 



TABLE OF CONTENTS. 

Chapter. Page. Plate. 

I. General Principles 7 

II. Fire, Projectiles and Penetration 11 

III. Field Geometry 15 1, 2 

IV. Hasty Intrenchments, Gun Pits and Epaule- 

ments 21 3, 4 

V. Clearing the Ground 28 5,6 

VI. Obstacles 32 7, 8 

VII. Field Works 39 9-15 

VIII. Working Parties.. . . 57 16 

IX. Revetting Materials and Revetments 61 17, 18 

X. Field Casemates and Magazines 73 19, 20 

XL Field Works in Combination 78 21 

XII. Siege Works 84 22,23 

XIII. Defense of Localities 88 24-29 

XIV. Use of Cordage and Spars 105 30-33 

XV. Spar Bridges 118 34-40a 

XVI. Floating Bridges 140 41-49 

XVII. Roads 168 50 

XVIII. Railroads 175 51-53 

XIX. Telegraph and Telephone Lines 186 54 

XX. Demolitions 191 55-57 

XXI. Camping Expedients 205 58-60 



WLJ^TSLXJAI^ 



OF 



MILITARY FIELD ENGINEERING. 



CHAPTER I.— General Principles. 

1.— Military Field Engineering may be denned to be the art 
of utilizing the materials at hand for the attainment of the secu- 
rity, effectiveness, health and comfort of an army in the field. 

The modern rifle has vastly increased the value of cover, both 
ia attack and defense, and rendered necessary the application of 
the principles of fortification to an army in the field. The result 
to be obtained in all fortification is to so strengthen a position, by 
artificial means, that a force occupying it may successfully resist 
or subdue another attacking it. 

2. — Fortification is divided into two general classes, viz.: 

(a)— Permanent. 

(h)— Temporary or Field Fortifications. 

With the former this manual has nothing to do. 

3.— The latter division includes three quite distinct classes. 

The first comprises all works devised for the temporary protec- 
tion of important points, such as cities, arsenals, bridges, fords, 
positions, etc., and are technically known as Field Works. 



8 General Principles. 

The second comprises the various devices of the engineer for 
reducing a fortified place by means of parallels and approaches, 
called Siege Works. 

The third division relates particularly to the quickly made 
defenses by which an army in the presence of an enemy protects 
itself; these are known as Battle Intreneliments or Hasty Intrencli- 
ments. 

4.— A Defensive Position is one affording protection from 
the shot and observation of an enemy and, at the same time, com- 
manding the ground in front, within range. 

A position of perfect defense is not possible, but the following 
general principles are to be fulfilled as nearly as circumstances 
will permit. 

(1) The defenders' position should conform to the special tacti- 
cal requirements of the occasion* and should be such as to favor 
the use of their relatively strongest arm. 

(2) It should be made impossible for the enemy to obtain nat- 
ural cover during his advance. In other words, the position should 
have a free field of fire. 

(3) The defenders should be protected from the fire and view of 
the enemy by cover so arranged as not to interfere with counter- 
attacks. 

(4) The advance of the enemy should be hindered by obstacles 
so arranged that he may be checked while under the fire of the 
defenders. 

(5) Communications should be such that the defenders may 
freely move from one part of the position to another, while the 
contrary should obtain with respect to the enemy's ground in 
front. 

The chief requisite of a defensive position is a free field of fire, 
especially at short and mid ranges. If the position is judiciously 
selected the field of fire will generally be obtained without much 
difficulty, but the advantages of the position and the effect of the 
fire may be enhanced by temporary fortifications. The cutting 
down of slight ridges which might afford cover for the enemy 



*A nure 1 v defensive nosition, for instance, might have its flanks resting r»n im- 
passable'obstac'es, and thus be secure from a turning movement, but this same 
position »~ight be found to be a faulty one were a quick offensive movement, by 
the defenders, contemplated. 



General Principles. 9 

within effective range or the removal of hedges, fences, etc., may 
sometimes be of more benefit than the actual preparation of 
defenses. 

In the present advanced state of efficiency of fire-arms, artificial 
cover is, however, of greater importance than ever before. Con- 
structed in the right place, at the proper time, field fortifications 
may render indispensable service, while their neglect may insure 
defeat. 

5.— While formerly it was the special province of the Engineer 
to lay out and supervise the construction of defensive works, it 
has now, under the changed condition of warfare, become the work 
of the Line as well, and it may be laid down as an accepted rule 
that the defensive arrangements for a given position are to be 
made by the troops which are to occupy it. 

These changes have affected the art in many ways. The field 
works now constructed are simpler, ruder, less regular, and less 
angular than before. An army in the presence of an enemy always 
fortifies, whether in camp, in bivouac, or in line. 

6.— Rapidity of execution renders necessary the adoption of 
fixed types of works in the exercises in time of peace; but these 
types will sometimes be susceptible of modification in their real 
application. However, even in war, the endeavor should be to 
approximate to the regulation forms, for they are deduced from 
experience and observation, and realize, as well as possible, for 
each particular case, the best conditions of resistance compatible 
with rapidity of execution. 

The advantage of regulation types is understood at once when 
it is borne in mind that, upon the battle-field, there should be no 
hesitation; everyone should stick to his individual role in order 
to unite efficiently in combined action. 

Thorough study and frequent practical exercises, conducted 
methodically, are indispensable in order to escape feeling one's 
way, with the loss of time that an insufficient instruction renders 
inevitable. Upon the battle-field a few minutes may decide the 
fate of armies in each other's sight. 

7.— Fortification, which at first glance may appear to dominate, 
as representing the "security" and "effectiveness" of an army, 



10 General Principles. 

the other and apparently less important subjects relating to health 
and comfort, is, however, so intimately connected with them that 
neglect of one may render all the others useless. Thus, "bridges," 
"roads," and "railroads" may, under certain conditions, relate par- 
ticularly to the effectiveness and security of an army, in con- 
nection with Fortification, while under other circumstances they 
may be as important as various "camping expedients" in the 
attainment of "health" and "comfort." 



CHAPTER II.— Fire, Projectiles and Penetration. 



8.— Fire as regards its direction is classified as follows: 

(1) Frontal, when it is delivered at right angles to the front 
of the enemy's line, and sometimes so termed when delivered 
straight to its own front. 

(2) Oblique, when the direction of the fire is at an oblique angle 
to the front of the enemy's line. 

(3) Enfilade, which is delivered from positions on the prolon- 
gation of the enemy's line. In this case, the line of fire sweeps 
the enemy's front. When fire is used to sweep along the front of 
a defensive line and thus enfilade the assailants as they approach 
the position, it is known as flanking fire. 

(4) Reverse, when delivered so as to strike troops or lines of 
defense from the rear. 

(5) Cross, when the lines of fire from different positions cross 
on or in front of the enemy's line. 

As regards its trajectory it is classified as 

(1) Direct, when .delivered at seen objects at moderate angles 
of elevation— in the case of artillery when delivered at seen objects, 
with service charges at elevations not exceeding 15°. 

(2) Indirect or Curved, when delivered with small-arms against 
an unseen object protected by a seen covering obstacle— in the case 
of artillery, as above, or with guns, howitzers or mortars with 
reduced charges at angles not exceeding 15°. Thus firing over an 
intervening hill at troops sheltered behind it would be an example 
of indirect fire. 

(3) High Angle, when used at angles exceeding 15°. 

(4) Grazing, when the projectile travels approximately parallel 
to the ground. 

(5) Plunging, the muzzle is required to be depressed. 

9.— The Artillery Projectiles used in the U. S. Army are shell, 
shrapnel and canister. 



12 Fire, Projectiles and Penetration. 

Shell.— Shell may be classified as common shell and torpedo 
shell. The common shell is "a hollow cast-iron or steel cylinder 
with an ogival head closed at one end and filled with powder." 
The torpedo shell is filled with gun-cotton, or other high explo- 
sive. Either shell may be characterized as a flying mine, the 
chief object of which is to destroy material objects at a distance, 
though the common shell may also be effectively used against 
troops. 

10.— Shrapnel differs from common shell in being filled with 
bullets, and having only a sufficient bursting charge to rupture 
the envelope and release the bullets, which then move with a veloc- 
ity which the projectile had at the moment of bursting. The bul- 
lets are assembled in circular layers and held in position by "sep- 
arators," which are short cast-iron cylinders with hemispherical 
cavities into which the bullets fit. The shrapnel for the 3.2 inch 
gun contain 162 bullets % in. in diameter, and weighing 41 to the 
lb. The total number of bullets and individual pieces in the shrap- 
nel is 201 when assembled, and many more after bursting. 

11.— Canister, which is practically obsolete, is made of sheet- 
iron or tin in the shape of an ordinary can, and is filled with bul- 
lets held in place by filling the interstices between the bullets with 
saw-dust, sulphur or rosin; the can is ruptured and its contents 
dispersed by the discharge of the piece. 

12.— The charges in the shell and shrapnel are exploded by 
means of a combination fuse; by combination fuse is meant one 
that may be arranged to explode the charge either on impact, by 
percussion, or at a given time by certain arrangement of the parts 
of the fuse. 

13.— Field Guns range up to 6000 yds., but will be seldom used 
at a range greater than 2500 yds. 

14.— The U. S. Magazine Rifle, when used as a single loader, 
has fired 21 aimed shots in one minute, and when used as a maga- 
zine rifle, 23 shots in one minute; its range is over 3000 yds. and it 
is sighted to 1900 yds. 

The average heights over which fire may be delivered are as 
follows: Man standing, 4 ft. 4 in.; kneeliug, 3 ft.; lying down, 1 ft.; 
field guns, 3 ft. 



Fire, Projectiles and Penetration. 13 

15.— The following thickness of material may be considered as 
proof against small-arm projectiles at all ranges: 

Sand 30 in. 

Earth 39 in. 

Boggy or turfy ground 60 in. 

Gabion filled with earth 1 

Well-made fascines 3 

Sand bag well packed, header 1 

" " " " stretcher 2 

Stacked sod 79 in. 

Packed snow 79 in. 

Soft wood 40 to 49 in. 

Oak or other hard wood 24 in. 

Grain sheaves piled 16 ft. 

Iron plate 7-16 in. 

Steel plate % in. 

♦Masonry brickwork with broken joints 20 in. 

Crib of broken stone 8 in. 

Against field artillery. 

Sand 10 ft. 

Earth 13 ft. 

Clay 17 ft, 

Snow well packed 27 ft. 

Masonry (for a short time) 40 in. 

*A wall two bricks thick, breaking the joints, will stop any one 
bullet, but after a time the bricks will be smashed and some bul- 
lets get through. 

A well-built wall with fine joints set in cement mortar, 9 inches 
thick, is practically bullet-proof. 

A 24 -inch sun-dried brick wall is fairly bullet-proof a short 
time after setting. 

15a. — The mean penetration of shells from siege guns, with a 
striking velocity of about 800 feet, is: 

6-inch 8- and 10-inch 
Guns. Guns. 

Feet. Feet. 

Sand, mixed with gravel 9.84 11.48 

Light earth 13.12 16.73 

Light earth, loose (newly stirred up) 14.76 20.34 

Clay (argillaceous earth) 21.33 27.89 



14 Fire, Projectiles and Penetration. 

Dimensions of craters made by 6- and 8.5-inch shells: 

6-lnch. 8.5-inch. 

Diam. Depth. Diain. Depth. 

Feet. Feet. Feet. , Feet. 

Clayey earth 16.48 4.9 22.3 6.9 

Calcareous sandstone 13.1 3.3 16.4 3.9 

Concrete 9.8 3 11.5 3.3 

Rough masonry 9 2 6.6 3 

Note. — With delayed-action fuses, shells burst after gaining a 

certain penetration. The maximum effect of the bursting charge 

will be found on the line of least resistance. 



CHAPTER III.— Field Geometry. 



16.— Before proceeding to that portion of field engineering 
which involves geometry some of its simplest applications will be 
explained. 

17.— Slopes. The usual description of a slope is by a fraction, 
the numerator being the height and the denominator the base. 
Thus, in PL 1, Fig. 1, the vertical height is l-6th part of the base, 
and the slope is read as 1 on 6. In Fig. 2, the slope is G on 1. 

18.— To lay out a Right Angle: First Method. Let A be a 
point in the line BC, Fig. 3. Lay off from A the equal distances 
AD and AE. With a radius greater than AD, and with D and E 
as centers, describe arcs cutting each other at X. Join X with A. 
Then is XA perpendicular to BC. 

Second Method. Find a point such that the distances are in the 
proportions of 3, 4 and 5: then will the angle included between the 
two shorter sides be a right angle. Thus (Fig. 4) with chain or 
tape measure the distance AD equal to 4 yds. Place one end of 
tape at D, the other at A, pulling it out and making XD equal to 5 
yds., XA equal to 3 yds. 

Third Method. At extremity of line, as A (Fig. 4), assume any 
point as C. Measure distance CA, set a stake on line BA at a dis- 
tance from C equal to CA, as D. Set a third stake on line CD at X, 
making CX equal to CD. Then will XA be perpendicular to 
BA. 

19.— To erect a perpendicular to a line from a point without. 
Let X (Fig. 5) be the point without, then, with X as a center, and 
a distance greater than XA as radius, describe an arc cutting BC 
at D and E. With D and E as centers, and with a radius greater 
than DA, describe arcs cutting each other at Y. Join X and Y. 
Then will XY be perpendicular to BC. 

20.— To bisect a given angle. Let BAC (Fig. 6) be the angle. 
With A as a center, and with any convenient radius, as AD, 
-2- 



PLATE 1 



Figure 1. 



Figure 2. 



X*'' 



Figure 3. 



B \D A 

Figure 4 



zV 



IE C 
x 

A 

\ 

3 \ 



Figure 5 




E ^^B 



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Figure 7 y yV\^ 




Figure 9. 



A ' C ' 



1 D ' B 



Figure 10. 




B D N A EC 



B D C 



Figure 11 



Y 




Field Geometry. 17 

describe an arc cutting AB and AC at E and D. With D and E as 
centers, describe arcs cutting each other at X. Join X with A. 
The line XA bisects the angle BAC. 

21. — To lay out an equilateral triangle constructing adjacent 
angles of 60° and 120°. Let AB (Fig. 7) be a given line. Lay 
off from B any convenient distance, as BE. Then, with B and E 
as centers, and a radius equal to BE, describe arcs cutting each 
other at D. Join D with E and B. The angles DEB, DBE and 
EDB are each equal to 60°. The angle AED is equal to 120°. 
Combining this method with that of slopes an angle of almost any 
number of degrees can be laid out. 

22. — To lay out an angle equal to a given angle. Let X 
(Fig. 8) be a point in the line AB, from which it is required to lay 
out an angle equal to OEC. Fix the points O and C at convenient 
distances from E. From X lay off Xg equal to OE. Then, with 
X and G as centers, and EC and OC as radii respectively, strike 
arcs intersecting at F. Join X and F. The angle FXG is equal to 
the angle CEO. 

23. — To draw a line parallel to a given line and at a given 
distance from it. Let AB (Fig. 9) be the given line. From any 
two points, as C and D, erect perpendiculars. On these lay off the 
required distance CE and DF. Join E and F. 

24. — To find the distance between any two points when it 
cannot be measured directly. First Method. To find AO, take 
a point B in line with AO and from this point (Fig. 10) lay off any 
convenient angle, as ABC. At D make EDC equal to ABC. Meas- 
ure BC, DC and DE, putting E in the line CO. From similar 
triangles 

BC X DE 

BO : BC :: DE : DC .'. BO = 

DC 

From the result thus found, subtract the distance AB. The 
remainder is the distance AO. 

Second Method. (Fig. 11.) Mark B in prolongation of the line 
AO. Assume any point as C. Lay off AF, making AC equal to 
CF: also BE, making BC equal to CE. Prolong EF until a point 
K is found in line with CO. Measure FK. This is the required 
distance. 



18 Field Geometry. 

25. — Areas. To find the area of a rectangle. Multiply the 
base by the height. 

To find the area of a trapezoid. Multiply the sum of the two 
parallel sides by the perpendicular distance between them and 
take half the product. 

To find the area of a triangle. Multiply the base by the alti- 
tude and take half the product. Or, 

Area = \/ s (s — a) (s — b) (s — c) 
in which s is the half sum of the three sides a, b, and c. Or, 

Area — % a b sin G 
in which a and b are two sides and C the included angle. 

26.— The Field Level (PL 2, Fig. 1) consists of three strips of 
wood, A, B and C, each % in. thick and 2 in. wide. A being 62 in. 
long, B and C each 44.42 in. The distance between centers on A is 
60 in., on B and C 42.42 in. This makes a right angle between B 
and C. There is a thumb nut at E ciamping the arm B to the arm 
A when the level is used. The screw at F projects, holding the 
arm B, when folded, up. There is a stud at H, affording an attach- 
ment for a plumb bob. There are permanent joints between B 
and C, and A and C. 

Fig. 1 shows the level and its joints, plumb bob for reading 
slopes, and spirit level. Fig. 2 shows side for protracting angles. 

27. — Uses of Level. The level may be used as follows: 

(1) As a spirit-level, the level being on the edge G. 

(2) As a square for setting out a right angle. 

(3) As a protractor. 

(4) For setting off slopes. 

(5) As a mason's level with a plumb bob. 



PLATE 2. 





PLATE 3. 



SHELTER TRENCH. 

- LYING.- 




7f|^'^!^%pP 



SHELTER TRENCH. 

-STANDING- 




SPLINTER PROOF, 

(earth cover omitted). 



Fig. 5 . SHELTER m SUPPORTS <m RESERVES. 




HEAD LOG and 
BRUSH-WOOD LOOPHOLE 



LOOP-HOLE 



$6<89T 



CHAPTER IV.— Hasty Intrenchments, Gun Pits and 
Epaulements. 

28. — The intensity of fire made possible by the fire-arms of 
to-day renders some form of shelter on the field of battle impera- 
tive. Circumstances may occur when advancing lines of skirmish- 
ers will find natural shelter, but in many cases artificial cover will 
have to be constructed on the spot. 

Fortifications used on the field of battle depend, as to their posi- 
tion, extent and use, on the ground; in conformity to this idea 
they are constructed at the time of the battle, and not before. 

They are called "Battle" or "Hasty" Intrenchments, and should 
fulfill the following conditions: 

(a) The thickness of earth embankment should be such that it 
will not be liable to penetration by small-arm projectiles or shrap- 
nel fragments. 

(b) The intrenchments should conform to the average heights 
over which men can fire in the various positions,— viz. : lying prone, 
1 ft.; kneeling, 3 ft.; standing, 4 ft. 4 in.; and at the same time the 
height of earth embankment above the natural surface of the 
ground should be small, for the reason that the trenches can thus 
be more easily concealed and are less liable to be struck by artil- 
lery projectiles. 

Hasty or Battle Intrenchments consist of cover for 

(1) Skirmishers, lying, kneeling or sitting. 

(2) Firing Line, Supports and Reserves, kneeling, sitting or 
standing. 

(3) Gun Pits and Epaulements. 

'.id. — The shelter trench for skirmishers lying down is shown 
in Tl. 3, Fig. 1. It gives earth protection of a thickness of 2% feet; 
this thickness of loose earth will stop small-arm projectiles under 
ordinary circumstances. The average time required by one man 
to make 5 ft. (2 paces) of this trench is, with large pick and shovel, 
15 minutes; with small intrenching spade, 20 to 25 minutes. 

The number of skirmishers that can use this trench is usually 
computed as two for each five feet of length, although three may 
occupy this space by lying partially on their left sides. In firing, 
the left elbow rests on the berm. 

30. — For men kneeling in two ranks, cover is gained by deep- 
ening the trench already dug to 1 ft. 8 in. and making it 5 ft. wide 



22 Hasty Intrenchments, Gun Pits and Epaulements. 

with an embankment in front having a height of 1 ft. 4 in. and a 
resulting thickness of about 5% ft. (Fig. 2.) 

The average time required by one man to transform 5 ft. of the 
trench "lying" into the trench "kneeling" is, with large pick and 
shovel, 25 minutes; with small intrenching spade, 45 minutes. 

Infantry in double rank kneeling can fire from this trench, the 
number of rifles being computed at 4 for each 5 ft. length of trench. 
The kneeling trench affords protection to men sitting, but hori- 
zontal fire from this position is impossible. The step at a would 
only appear in the converted trench. 

31. — Cover standing is obtained by deepening the kneeling 
trench to 4 ft., leaving a step 20 in. high and 3 ft. wide next 
the front wall, so as to facilitate leaving the trench to the 
front and at the same time allowing a protected passage in 
rear. The step serves as a banquette for men firing over the 
embankment. 

The embankment is given a height of 2 ft., the resulting thick- 
ness being about 5% ft. (Fig. 3.) 

The average time required by one man to transform 5 ft. of 
the trench "kneeling" into the trench "standing" is, with large 
pick and shovel, 1 hour.* 

32. — When isolated trenches for single skirmishers lying are 
desired, they should be made with the same section as that shown 
in Figure 1 and have a length of 1 pace. Isolated kneeling trenches 
for two men should also have a length of 1 pace, but the 
rifle pit or isolated shelter standi no should be 5 ft. in length on 
account of difficulty in constructing a smaller one. The last read- 
ily accommodates three men, two of whom can fire over the 
embankment, while the third, standing in the 4 ft. trench, pro- 
tects the flanks. 

33. — When necessary to intrench supports and reserves, the cover 



:: 'The ordinary form of Spanish hasty intrenchment for fire, standing and cover 
sitting, kneeling or crouching is a trench about two feet wide and four feet deep, 
having vertical sides and no embankments. This type of trench does not readily 
permit relieving or re inforcing the occupants an^. as it is too narrow to permit 
carrying the wounded out, there results extreme suffering, since the injured must 
lie at the bottom and run the risk of being trampled upon. This trench has the 
advantage however of affording a small target for the enemy's artillery. 

The Hermans claim that the surface presented to shrapnel bullets by a man 
lying down is practically the same as a man standing in the open; therefore they 
do not believe in broad shallow trenches They advocate the making of trenches 
in the natural soil with the fresh earth carried away, or u?ed for dummy trenches 
so as to deceive the enemy's artillerists and prevent execution from shrapnel fire. 



Hasty Intrenchments, Gun Pits and Epaulements. 23 

kneeling or standing should be used in parallel rows close to one 
another. (Fig. 5.) 

In the construction advantage should be taken, where possible, 
of plows for loosening the earth. Two or three plows following 
each other at intervals can be used to great advantage. 

34. — The trenches here illustrated are all made on level 
ground and are simply types showing the best forms and giving 
general ideas as to the time required to construct cover.* On 
slopes they must be modified so that the tops of the embank- 
ments are, in general, parallel to the ground; they may also be 
varied according to the kind of earth, sand requiring less thick- 
ness of embankment and gentler slopes than clayey soil, while 
sod mixed with earth allows greater penetration than earth 
without it. 

35. — The location of trenches depends primarily on tactical 
situations, and secondarily on the nature of the ground. 

Primarily, they should always occupy a position giving the 
greatest development of fire, and hence are generally located 
near the crest of tlie most abrupt slope— i. c., near the "military 
crest." (See par. 153.) The exact position is determined by plac- 
ing the eye at a distance above the ground equal to the proposed height 
of embankment, and then selecting that line which gives a clear field of 
fire to the front. ^ 

As to the secondary consideration, it is desirable in locating 
trenches to avoid stony ground and that close to the edges of 
woods, the former on account of the liability to flying frag- 
ments should the embankment be struck by an artillery projectile, 
and the latter by reason of the difficulty in constructing the 
trenches. 

36. — Intervals in line of trenches. In all trenches except 
those for skirmishers lying down, intervals in the line should be 
left for the passage to the front of artillery and cavalry— this 
is especially necessary when cover standing is used. The inter- 
vals may vary in width according to circumstances, but should 
never be so wide as to preclude their defense by the trenches 
adjoining the opening. 

37. — Splinter-proofs. When troops are required to remain 



*Cover from view only can, of course, be obtained much more quickly, but a 
penetrable cover is hardly more than a target to invite an enemy's fire. 



24 Hasty Intrenchments, Chin Pits and Epaulements. 

in the trenches for any considerable period, they should be pro- 
vided with splinter-proofs or shelters of some kind. Planks, old 
lumber, doors, etc., or, in their absence, small poles, may be used. 
They should be laid with one end on the embankment, the other 
resting on the ground in rear of the trench, and then covered with 
3 or 4 inches of earth. This defense, while not proof against burst- 
ing shells, will protect the men from dropping bullets and shrapnel 
fragments. (Fig. 4.) 

38. — Concealment of shelter trenches. Endeavor should 
always be made to disguise the location of shelter trenches 
by covering the sides toward the enemy with branches, weeds, 
sod, etc. 

39. — The advantages and disadvantages of the shelters for 
men lying and kneeling may be briefly summarized as follows: 

Advantages. 

(1) They present but little difficulty to the advance of the 
defenders' cavalry or artillery over them, and are easily sur 
mounted by the occupants when the advance is ordered. 

(2) They will stop rifle bullets. 

(3) They offer but a small target to the enemy's artillery fire. 

(4) They are quickly and easily made. 
Disadvantages. 

(1) The embankmeifts being low, the field of fire may be lim- 
ited by small folds in the ground (care in selecting their position 
may partially remedy this disadvantage). 

(2) In wet weather they may become untenable by reason of 
mud. 

40. — Loop-holes may be provided by half imbedding head-logs 
in the embankment, or resting them on sand-bags on top of it, ana 
leaving spaces beneath for the rifle. Or the loop-hole may be 
formed with four sand-bags, as shown in Fig. 7. Brushwood may 
also be used with an earth cover, either alone or in connection with 
a head-log, as shown in Fig. 6. 

Loop-holes for rifles splay inward, for field guns, outward. 

The best practiee is not to use head-logs or loop-holes (unless in 
case of an inferior force acting solely on the defensive), as their 
use impels men to hesitate to leave cover when the advance is 
ordered. 



PLATE 4. 







FIGURE 3. 



FIGURE 5. 



"" iTTi" 



+ 5' 6" 








FIGURE 2. 




*3'6-* 




^6 Hasty Inirenchments, Gun Pits and Epaulements. 

40a. — Cover for guns may be obtained in two ways. 

(1) By means of Gun Pits; made by digging a hole of a size suffi- 
cient to partially conceal the gun and gun detachment, and form- 
ing an embankment in front with the excavated earth. (PI. 4. 
Figs. 1, 2 and 3.)* 

(2) By means of Gun Epaulements; made by constructing an 
embankment in front of the gun which rests on the natural surface 
of the ground. In this form the gun detachment would be par- 
tially sheltered in the pits from which the earth for the embank- 
ment is taken. (Figs. 4 and 5.) . 

Circumstances would control the selection of the kind of cover, 
if any, for field guns. The disadvantages of gun pits are the same 
as those of shelter trenches, but pits give more complete protection 
to the gun. (See par. 153.) 



►Figs. 1, 2 and 4, PI. 4, are from U. S. Artillery Drill Regulations. 



PLATES. 




CHAPTER V.— Clearing the Ground. 



41. — The tools more especially used in the field may be divided 
into two classes. 

(1) Intrenching tools, such as the pick, the shovel (long and 
short handled, the spade, the picket shovel, and the hunting knife. 

(2) Cutting tools, such as the ax, the hand ax, the log saw, 
the hand saw, the linked felling saw, the gabion knife (pruning 
knife), the hunting knife, the bush hook and the wire cutter. 
(PI. 5 and 6.) 

42. — The choice of a defensive position in which the foreground 
is free from obstructions and favorable to the defenders' fire is of 
the utmost importance: more or less clearing, however, will usu- 
ally be necessary. Clearing must be systematically done, and, as 
in all other work, should be undertaken by complete organizations 
or parts of organizations under their own officers. 

43.— The extent (theoretical) to which the foreground should be 
cleared is equal to the effective range of the defenders' weapons. 
Practically, as wide a space within this limit, is to be cleared, as 
is consistent with the time and labor available. Brushwood and 
standing timber most often screen the enemy's advance and steps 
should be taken to remove them. 

44. — The tools usually employed in felling heavy timber are 
the ax and the log saw, the former being the most common, al- 
though inexperienced men acquire familiarity with the latter more 
quickly. When using the ax the cut should be commenced on the 
side tpward which it is desired the tree should fall, ropes being 
used to incline it in that direction, if necessary; if immaterial 
which way the tree falls, then attack it on the side toward which 
it learns; after cutting it a little more than half through change 
over to the other side and commencing about six inches higher 
up, cut until it falls. In using the saw it may be necessary to 



Clearing the Ground. ' 29 

wedge the cut or use other means in order to keep the saw free: 
the teeth should be set wide. 

Both saw and ax may be used, in which ease the ax should be 
used on the side toward which the tree is to fall and the saw on 
the other side. (PL 6.) 

45. — Trees would ordinarily be cut within a foot of the ground 
because a greater height would afford cover. A man should cut 
down a hard wood tree 1 ft. in diameter in 10 minutes and one of 
soft wood of the same size in one-third the time. The hand ax, 
hand saw, and hunting knife arc useful in felling small trees, ropes 
being attached to bend them, and the cut being made on the 
convex side. 

Felled timber must be removed, if of such a size as to afford 
shelter to the enemy. It is utilized in making field casemates, 
magazines, etc. 

46. — Brushwood can be cleared at the rate of about 12 sq. yards 
per man per hour. The men should be extended at about 4 paces 
interval, using the bush hook, hatchet, or hand ax, together with 
the gabion or hunting knife. 

47. — Grain, grass, or weeds must be trampled by men in line, 
mowed, or burnt. 

48. — Hedges, fences, and walls, if not perpendicular to the 
front, must be removed. Live hedges should be pulled to one side 
in order to give the axmen greater freedom. (PI. G.) Fences can 
ordinarily be demolished with axes, walls by battering them down 
or blowing them down with explosives. (Chapter XX.) 

Buildings may be battered down, burned, or demolished by 
explosives according to circumstances. In the case of buildings 
and walls it will usually be necessary to remove the debris, which 
can be used for filling hollows. 



PLATE 6. 




Wire Cutter. 



\ = )'~* — yrv4vvvvvvvWvvTArvvvy/ww VWvvvvvWv^WvTr^nn/vTrv n \^vTrv>^ — ^y 



Linked FeLltnjnr Saw. 



/KuQrur. 



o 



~~t In fa n try Sp ct cte . 




% EUROPEAN. 



*». 



PLATE' 7. 



"Figure 1 



Figure 2. 




Figure l2f 

-3- 



Figure 13. 



CHAPTER VI.— Obstacles. 

49.— Obstacles have for their object the holding of the enemy 
under fire while checking his advance and breaking up his 
formation. 

(1) They must be within the effective zone of the defenders' fire 
and must be so arranged as to offer the least obstacle possible to 
an advance from the side of the defense. 

(2) They must be concealed as far as possible from the view of 
the assaulting party, so that they may come upon them as a 
surprise. 

(3) They must be difficult of removal under fire, and, if possi- 
ble, should be of such construction as will necessitate the use of 
tools not usually carried by troops. 

(4) They should, if possible, be so placed as to be secure from 
the fire of the enemy's artillery, and so constructed that, if struck 
by his projectiles, they will suffer small damage. 

(5) They must offer no shelter to the enemy. 

50.— Abatis, on account of the ease with which it can be con- 
structed, is the obstacle most used. 

It consists of branches of trees about 15 feet long, laid on the 
ground, butts pointing to the rear, all small twigs being cut off, and 
all large branches pointed and interlaced. The abatis should be 
5 feet high. 

The branches are secured to the ground by forks, wire, or by 
logs laid over the butts of the branches. The use of wire to hold 
down the branches is recommended, and when used should be also 
passed from branch to branch so as to form an additional en- 
tanglement. When more than one row of abatis is used the 
branches of one row overlap the butts of the next one in front. 
(PL 7, Figs. 1 and 2.) 

The abatis most easy of construction is that made by felling 
trees towards the enemy in such manner as to leave the fallen 
part still attached to the stump; the branches are then pointed as 
described before. (Fig. 5.) This is called slasMng. 

51.— Abatis is often placed in the front of works when the 
ditch is so shallow as to present little or no obstacle to an assault. 
When so used they are placed upright and well tamped in. In all 
cases, especially when small branches are used, it is better to sink 



Obstacles. 33 

the butts in triangular pits, and, when the branches are in place, 
fill in with earth and tamp well. (Figs. 3 and 4.) 

In all cases where exposed to artillery fire a glacis should be 
constructed in front of an abatis, so as to protect it from injury. 

52. — Low Wire entanglements are formed by driving into the 
ground stakes projecting about 18 in. The stakes should be driven in 
rows about 6 feet apart, the stakes in each row being opposite in- 
tervals in adjacent rows. The heads of the stakes are connected 
by stout wire wound around them. To make this more effective, 
do not clear the grouud, but allow bushes, brush, etc., to remain in 
place. (Fig. 6.) Use 1 ft. of wire to 1 sq. foot of ground covered. 

53. — High Wire entanglements are constructed in the same 
manner, except that the stakes should be at least 4 ft. high, and 
placed 6 to 8 feet apart. The head of each stake is connected 
with the foot of the stake diagonally opposite, the line of posts in 
front and rear being finished off as fence panels with barbed 
wire. The use of barbed wire is not advised for the interior 
crossed work on account of the danger and difficulty in working 
with it. 

Roughly, 1 yard of wire is necessary for each square foot of 
entanglement. Ten men can make about 9 square yards of this 
entanglement in one hour. This work does not require trained 
men. Wire entanglement, either high or low, is useful on the 
glacis of field works, as it holds the attacker under fire at the most 
favorable point. (Fig. 7.) 

54. — Palisades consist of rows of trunks of trees or of squared 
trunks, 8 or 10 feet high, planted close together and pointed on 
top. When material is at hand, ribband pieces should be spiked 
on the inside along their tops about a foot or two below the 
points to hold them steady. They are used to advantage in the 
bottoms of ditches or to close the gorge of field works. (PI. 8, 
Fig. 1.) 

55. — Fraises are palisades arranged horizontally or much in- 
clined and nre often used at the foot of the exterior slope and at 
the top of the counterscarp; in the first position they point down 
and in the second upward. In each case, the ribband or strip is 
spiked on underneath and laid against the ground near the edge nf 
scarp or counterscarp, as the case may be, another one being spiked 



PLATE 8, 




Obstacles. 35 

to the inner end of the f raise on top; thus the outer ones give good 
bearing surfaces and do not break up the crest, and the inner one 
gives a bearing for staking and tying down. The slopes described 
above are given so that unexploded shell will always roll away 
from the parapet. (PL 7, Figs. 9, 10 and 13.) 

Fraises may with advantage be made of barbed wire in the 
form shown, care being taken that all wire when finished is on 
top of the wooden supports. The advantage of this variety of 
fraise is that it is little damaged by artillery fire and is very diffi- 
cult of removal. (PI. 7, Fig. 13.) 

When time is pressing fraises may be made of branches of trees 
with the butts well sunken and staked down. (PI. 7, Fig. 12.) 

56. — Crows' feet, Chevaux-de-frise, and plunks full of spikes have 
been used in the past as obstacles to an advance, but the two 
former are not now T issued for use in our service, and the latter is 
one not easily made in the field. Such obstacles require much 
time and material in their construction and are not treated of 
here, as they do not fall properly in the domain of Field Engineer- 
ing; their value in any event is not commensurate with the diffi- 
culty of their preparation. (PI. 8, Figs. 2 and 6.) 

57. — Small Pits or troup cle loup are square on the top, 3 feet 
on a side, and are pyramidal in shape; they are 2 ft. 6 in. deep, and 
have a pointed picket driven in the center of each. 

In digging these pits a glacis should be formed in front of the 
row T nearest the enemy, and, to avoid filling the pits with earth 
thrown from the others, the row farthest from the glacis should 
be commenced first. One man can make 10 pits per day in easy 
soil. (PI. 7, Figs. 8 and 11.) 

Small pits may be surmounted by a low wire entanglement, 
making a very serious obstacle. 

58. — Fords may be made impassable by strewing them with 
harrow T s, points up. 

59. — A Fougass is a mine so arranged that upon explosion a 
large mass of stones or shells are projected towards the enemy. 
(PI. S, Fig. 3.) 

To make a fougass, dig a hole in the shape of a frustum of a 
cone, inclining the axis in the direction of the enemy, so as to 
make an angle with the horizon of about 45 degrees. The sides 



36 Obstacles. 

should splay outwards at an inclination of 12 degrees from the 
axis. The powder charge is placed in the bottom of the hole- 
preferably in a box— and in front of this a platform of wood 
about 3 inches in thickness: on this are piled stones, brick, etc. 
The mine is exploded by means of electricity or common fuse. 
Care must be taken in digging the hole for the fougass that the 
line of least resistance is in all cases in the axis of the hole; to be 
sure of this, throw the excavated earth upon the crest towards the 
defenders' side and ram well, allowing earth to enclose the sides of 
the excavation in the manner shown in cut. 

Fougasses are useful in defending boat-landings, roads, etc. 

The following empirical formula may be taken for determining 
the charge of powder for fougasses: P = -^, in which P and s 
represent the weight in pounds of the powder and stone. 

When broken up, a cubic foot of limestone weighs 96 lbs. 

60. — Land Mines are small mines placed in the line of ad- 
vance of the enemy and exploded either by electricity or fuse 
from the defense. The small mines are made by digging holes 
from 2 to 3 yards deep, placing the charge in a box in a recess 
excavated in one side of the hole, and refilling with the excavated 
earth, tamping well. The wires are carried back in a small trench 
to the work. In common earth, the charge for 2 yards deep is 
about 25 lbs., and for 3 yards deep about 80 lbs.; the diameter 
of the crater formed will be about twice the depth of charge. 
(PI. 8, Fig. 4.) 

*To determine the quantity of explosive necessary for use in 
a "common" mine, multiply eleven-sixths of the cube of the line 
of least resistance in yards by the quantity of explosive required 
to throw out one cubic yard. 

Quantity of gunpowder necessary to throw out a cubic yard of 
material (Macaulay): 

Pounds. Ounces. 

Light sandy earth 1 13 

Hard sand 2 

Fat earth mixed with sand and gravel 1 10 

Wet sand 2 2 

Earth mixed with stone 2 4 



* "Military I,and Mines," Mercur. 



Obstacles. 37 

Pounds Ounces. 

Clay with tufa 2 8 

Fat earth mixed with pebbles 2 12 

Rock 3 10 

New brickwork or masonry 2 2 

Inferior brickwork cr masonry 2 11 

Good new brickwork or masonry 3 10 

Good old brickwork or masonry 4 11 

The following formula gives the relation beween the charge 
for common and overcharged or undercharged mines: 

c=.c ( 7 / 8 f;+y 8 ) 3 ; 

C = charge for common mine (lbs.); 

r = radius of crater; 

C = charge for undercharged or overcharged mines (lbs.); 

L = length of line of least resistance. 

The following formula give charges for common mines: 

With explosive gelatine, 

C-l-17 (L + % (r — L) )3; 

With gunpowder, 

C = l-10 (L 4- % (r — L) )3; 

C = charge in pounds; 

r = crater radius in feet; 

L = line of least resistance in feet. 

In common mines, 

L = r. 

61. — Barricades are used to prevent the passage of the enemy 
through roads, streets, and defiles generally. 

They may be made of any material at hand, paving stones, 
overturned carts, barrels filled with earth, stones, and articles of 
like nature. They should be built so that a passage is always left 
for the defenders, but means should be at hand to close the open- 
ing quickly— a wagon may be used for this purpose, being drawn 
away from the opening when a passage is desired. 

The houses on either side should be loop-holed and used to 
flank the defense. Overturned w^agons, broken furniture and 
debris from the adjacent houses make a very good obstacle and 
should be placed in front of the barricade to ward off cavalry 
charges. (PI. 8, Fig. 5.) 



StATE.9. 




CHAPTER VII.— Field Works. 

62. — When a position is to be held for a considerable period and 
when time is available, more deliberate defenses than the Hasty 
or Battle Intrenchments (Chapter IV.) are constructed. These are 
known as Field Works and usually require a minimum of G hours 
for construction. The conditions to be fulfilled, besides those nec- 
essary for a defensive position (Chapter I.), are. 

(1) That they must afford protection against both rifle and 
artillery fire. 

(2) That they must be of suitable size for the garrison that is 
to occupy them. 

(3) That they should have suitably constructed casemates to 
sheltef the garrison at night. 

Field works may be constructed for the defense of a single ob- 
ject, as a bridge, a ford, etc., or they may occupy the key points in 
a long line of defense, in which case they should be located so as 
to afford mutual protection, the intervening space either being left 
open or occupied by shelter trenches. 

Before proceeding to the study of Field Works, a brief synopsis 
of the technical terms used in connection with them will be 
necessary. 

63.— A Parapet is a bank of earth thrown up to cover the 
defenders while firing. 

64. — The Trace of a work is its outline in plan: the term is 
often applied to the horizontal projection of its interior crest. 
(PI. 9, Fig. 1.) 

65. — The Profile is a cross-section of the work made by a plane 
perpendicular to the interior crest. (Fig. 2.) 

In the profile, the various parts are named as follows: 
n. Banquette slope, e. Exterior slope. D. Ditch. 

b. Banquette tread, f. Berin. i. Interior slope of glacis. 

c. Interior slope. g. Escarp. k. Glacis. 

d. Superior slope. h. Counterscarp, t. Trench. 

66. — The Interior Crest is the intersection of the Interior 
and Superior slopes: sometimes called the magistral line. ("a" 
Fig. 1.) 



40 Field Works. 

67. — The Exterior Crest — that of the Superior and Exterior 
slopes, ("b" Fig. 1.) The thickness of parapet is the horizontal 
distance between interior and exterior crests. 

68. — A Traverse is a bank of earth inside a work to protect 
some portion of it from direct fire. When the protection afforded 
is from reverse fire, the traverse is sometimes called a Parados. 
(Figs. 3 and 4.) 

69. — An Embrasure is a revetted opening in the parapet, 
through which field guns may fire. It is said to be Direct or 
Oblique according to whether its axis is perpendicular or inclined 
to the line of parapet. 

70. — A Grun Bank is a raised mound, by means of which field 
guns may fire over the parapet. Guns thus placed are said to be 
en barbette. 

The relative advantages of Embrasures and Gun Banks are as 
follows :— 

Embrasures afford greater protection to the gunners, but 

(a) They afford a very limited field of fire. 

(b) They weaken the parapet and require frequent repairs. 

(c) The place of the gun when not in action cannot well be used 
by Infantry. 

The conditions as to Gun Banks are the converse in each case. 

71. — The Command of a work is the height of its interior crest 
above the ground on which it is constructed, ("m" Fig. 2.) 

72. — Its Relief is the height above the bottom of the ditch, 
("o" Fig. 2.) 

73.— The Plane of Site is a plane tangent to the ground on 
which the work is constructed. 

74. — The Terreplein is the surface of the ground inside the 
work and does not, of necessity, coincide with the plane of site, 
since the whole interior of the work — i. e. 9 the terreplein— may be 
lowered for the purpose of securing more cover. 

When the banquette tread is more than 2 feet above the terre- 
plein, its slope may be stepped with fascines or planks: this has 
the advantage of giving more interior space, but tends to produce 
confusion on the part of the defenders, especially in a night 
assault. 



Field Works. 41 

75. — The interior slope is usually made as steep, up to four on 
one, as the revetment will stand. 

76. — The superior slope is necessary in order to secure the best 
fire effect on the ground immediately in front of the work. It 
weakens the parapet near the interior crest, however, and this 
defect increases as the slope is made steeper; hence, it should be 
as slight as is consistent with good fire effect. 

The degree of this slope is regulated by the principle that fire 
from rifles resting on its surface should not pass more than three 
feet above the glacis, or, when there is no glacis, above the outer 
edge of the ditch. It will thus depend on 

(1) The command of the work. 

(2) The inclination of the plane of site. 

(3) The distance from the interior crest to outer edge of ditch. 
The slope should not exceed one on four; one on six (normal) is 

better, and then, if necessary, make a glacis of the requisite 
height. 

77.— The exterior slope should be as gentle as two on three, if 
possible, owing to the fact that steeper slopes are soon destroyed 
by artillery fire. 

78. — The Berm may be as great as 6 ft. in width; ordinarily it 
would not be greater than 2 ft., while in favorable soil none may 
be left at all. 

Advantages of berm: 

(1) It relieves the edge of the ditch from the weight of the par- 
apet and thus prevents caving, in loose soil. 

(2) It enables the parapet to be thickened. 
Disadvantages: 

(1) It affords a footing in an assault. (This, however, may be 
partially remedied by use of obstacles.) 

79. — The slope of the escarp and counterscarp should be equal 
to or greater than the exterior slope, the counterscarp being as 
steep as the earth will stand. 

80.— The Glacis should be parallel to the superior slope, in 
order to get the best fire effect from the crest. 

81. — If the parapet does not require much earth, and the ditch 
is required as an obstacle, it may be made triangular in cross-sec- 



42 Field Works. 

tion. This form gives the greatest depth and prevents the assail- 
ants from forming in the ditch, but it is difficult of construction. 
Eight feet may be taken as the extreme depth of ditch and twelve 
feet as the extreme height of parapet. The width of the ditch 
varies with the amount of earth required— 12 ft. at the top being 
a minimum. 

A parapet with trench and ditch affords cover in the shortest 
time possible: each foot of depth in the trench means 2 ft. of 
cover, plus the additional protection afforded by the earth from 
the ditch. 

A parapet with ditch alone affords greater cover to the ground 
in rear and better command of ground in front, but its height 
makes it more conspicuous. 

82.— Referring to traces of various works (PL 9, Fig. 5)— 

a, is a salient angle, 
a' is a shoulder angle. 

b, is a reentrant angle. 

c, c, c, are faces. e, e, is the gorge. 

d, d, d, are flanks. f, is the capital. 

83. — Field Works are classified with reference to their 
trace, as 

(1) Open, which have thick parapets on exposed sides, the rear 
or gorge being open. 

(2) Closed, in which the thick parapet is continuous. 

(3) Half-Closed, which only differ from the "open" in that 
the gorge is closed by obstacles, stockade work, or shelter 
trenches. 

Advanced works within rifle range of the main defensive line, 
as well as those in positions where the flanks are secure (as a 
bridge head), should usually be "open." Works in main line and 
advanced works beyond rifle range should be "half-closed"; those 
in isolated positions or on the flanks of a defensive line— "closed." 

Open works have the advantage over closed, of affording greater 
freedom of movement to the defenders, and, in the event of cap- 
ture, of being exposed to fire and assault from the works in rear. 

Closed works, while affording greater protection from assault, 
are liable to have their parapets exposed to enfilade or reverse fire, 
besides which the available interior space is much reduced. 



PLATE 10. 




44 Field Works. 

84. — Forts and Redoubts (Closed Works) are distinguished 
by the former having reentering angles, thus affording defense 
of the ditch from the parapet, both conditions being lacking in 
redoubts. 

Redoubts, as compared to forts, are of simpler trace, do not re- 
quire so large a garrison, and afford better frontal fire; but, as 
they have no ditch defense (unless caponiers and counterscarp 
galleries are constructed), they should be traced to support one 
another. 

85. — With respect to caponiers (PI. 20) and counterscarp gal- 
leries—the former, if sunken, as is usually necessary for protection 
against artillery fire, may become untenable in rainy weather; 
while communication with the latter is difficult and may, by the 
enemy, be rendered impossible. The objections to these forms of 
ditch defense are so great, and their use so limited, where proper 
frontal fire and obstacles are possible, that their construction is 
seldom necessary. 

86.— The Sector of Fire is a term used to designate the angular 
space in front of a work which is swept by its fire (30° on each 
side of a perpendicular being considered the limit of oblique rifle 
fire.) Thus, a straight line of parapet has a sector of fire of 60° 
(PI. 10, Fig. 1), while, in a redan, it varies with the angle at the 
salient. With a salient of 120°, the sector of fire is evidently 120° 
(Fig. 2); with a 60° salient, there will be an undefended space of 
00°. (Fig. 3.) This undefended space may be done away with by 
blunting the redan. (Fig. 4.) A redan with shoulder angles 
(Fig. 5) furnishes a ditch defense in front of the shoulders and does 
away with part of the dead space in front of the salient, but it is 
difficult of construction and is not usually resorted to. 

87.— For reasons given in Chapter XI., it is often desirable to 
place the guns outside the work; in which case some plan like 
Fig. 6 may be adopted, the single line representing a shelter 
trench. 

88.— Defilade of Field Works. In order that Field Works may 
fulfill the condition of screening the occupants from the fire and 
view of an enemy, the problem of defilade arises. 

This may be defined as the operation of regulating the direction 
and command of the earth cover so that the interior of the work 
is protected from the direct fire of an enemy. 



Field Works. 45 

The problem resolves itself into two distinct parts— 

(1) Defiladiny in plan. 

(2) Defilading in section. 

89. — Defilading in plan. This involves the selection of the 
trace of the work (its position having been previously chosen). 
The trace will vary with the plane of site, the terrain in the im- 
mediate vicinity, the proximity of high ground that the enemy 
may occupy, and the time available for construction. A plane of 
site sloping to the rear is obviously the easiest to defilade, and 
one sloping toward the enemy the most difficult. Salients should 
occupy commanding ground, the lower portion being taken for 
the reentrants or for the gorge. The longer faces of a work should 
lie in the direction of lower or inaccessible ground, so that they 
cannot be enfiladed. 

With commanding ground in front, the work is more difficult 
to defilade in proportion to its depth; therefore, have longer faces 
opposed to the high ground and make the work as shallow as is 
consistent with other conditions. 

As a rule, the longer faces of a work must lie so that the de- 
fenders can bring as direct a fire as possible in the direction of 
expected attack. 

All the foregoing conditions as to defilading in plan cannot, in 
the usual case, be satisfied, but the object to be attained must be 
kept constantly in view, and, in selecting the trace for a work, an 
officer's ability will be shown by the skill with which he harmon- 
izes the various diverse requirements. 

After the careful selection of the trace, as already indicated, 
and marking it by pickets, the problem is completed by defilading 
the proposed work in section. 

90. — Defilading in section. With a horizontal site and only 
level ground toward the enemy, a constant command of 8 ft. is 
sufficient to protect the whole interior of the work. 

On an irregular site, or when necessary to place a work in a 
position commanded by higher accessible ground, the necessary 
protection of 8 ft. may be attained in one of three ways— 

(1) By raising a parapet. 

(2) By lowering the terreplein. 

(3) By use of traverses, parados, bonnets, etc. 



PLATE H 



Figure I. 




Figure. 2. 







Figure 3. 



_/ Jnfcrw 'Gvst ~~ 







Figure 4 . 



*'* 




Field Works. 47 

To determine how much protection is needed, suppose, for ex- 
ample, the proposed work is a lunette. Plant poles at the salients 
of sufficient length to reach the interior crest of completed work. 
Place two pickets at the gorge, about 6 ft. apart, one on each side 
of the capital, and a third 8 ft. to the front. Tie a string to the 
rear pickets, 3.5 ft. from the ground, the string passing round the 
third stake. (PL 11, Fig. 2.) Taking position behind the horizontal 
string, have an assistant move the string on the forward picket 
until it comes into the plane fixed by the eye, the horizontal string 
and the highest point of the dangerous ground. This plane, 
which is now established by the string triangle, is called the tan- 
gent plane. A plane parallel to this and 4.5 ft. above it is known 
as the plane of defilade. (Fig. 1.) The proper height of parapet at 
the salient and shoulder angles is now fixed by sawing off the 
poles 4.5 ft. above the points in which the tangent plane cuts them. 
This will evidently give 8 ft. cover at the gorge, at which point 
the height of parapet of the flanks is 8 ft. 

If it is found that the required height of parapet exceeds 12 ft., 
the plane of defilade may be lowered not to exceed 1.5 ft. This will 
still give 6.5 ft. protection at the gorge. 

If this proves insufficient, either traverses must be resorted to 
or the terreplein at the gorge lowered. 

91. — To defilade a work from two or more heights, the plane 
must be tangent to the two heights to which angles of elevation 
are the greatest. As three points fix a plane, it follows that the 
tangent plane w r ould usually contain but a single point of the 
string at the gorge; hence, the problem is solved by reversing the 
string triangle — i. e., fixing the apex at the gorge 3.5 ft. above the 
ground, and the two extremities of the base within the proposed 
work and far enough apart to allow the two heights to be seen 
between them. An assistant at each of the forward stakes ad- 
justs the string as directed. (Fig. 3.) The problem is then com- 
pleted as in the previous case. 

92.— It is sometimes advisable, when a single plane of defilade 
gives too great a command, to use two planes; the portion of the 
interior of the work on the side toward H (Fig. 4) being defiladed 
from it, and that on the other side from the height H\ This 
method exposes the faces and flanks to reverse fire and renders 
traverses (parados) necessary. 



48 Field Works. 

93. — The height of a traverse (which should be such that a 
shot grazing it will pass 2 ft. above the parapet it is to cover) is 
found as follows: 

Assume that the traverse is to be on the capital of a lunette. 

The problem of direct defilade with two planes having been 
solved, and the poles at angles of the works having been sawed off 
to indicate the proper height of interior crest in order to defilade 
the work as far as the capital, the height of traverse to protect a 
flank from reverse fire is found thus: Measure down from the 
tops of the poles at the extremities of the flank any convenient dis- 
tance, as 3 feet,* mark the points and connect them by a string. 
This string and the opposite height determine a plane which will 
cut rods held vertically on the capital, at a distance of 5 feet below 
the required top of the traverse (2 ft. plus the distance measured 
down on the poles). Proceed in a similar manner, using the other 
hill and its opposite flank. The greater of the two results fixes 
the height of that portion of the traverse. In the same manner, 
its height to protect the faces from reverse fire may be found. 
By reference to Fig. 4 this will be readily understood. 

This method, while not absolutely accurate, will give results 
near enough for all practical purposes, with the error on the side 
of safety. Traverses or Parados are the usual protection against 
reverse and enfilade fire, and, although sometimes used to protect 
parts of a work from direct fire, this is usually attained either by 
raising the parapet, by lowering the terreplein, or by both these 
methods combined. 

94.— Profiling. After the trace of the work has been decided 
upon, the problem of defilade solved, the poles at the angles cut 
off as indicated, and the cross-section of the parapet decided upon, 
the next step is to erect profiles which shall correspond to this 
cross-section. These profiles are, if practicable, to be made of 
strips or battens 1 in. x 2 in., and placed at intervals of about 10 
yds. along each face and flank, as well as at each angle. 

For parapets not over 6 ft. in height, stakes may at once be 
driven into the ground and strips nailed to them, but for higher 
parapets it is more convenient to make the profile on the ground, 
merely driving short pickets in place of the long stakes in the first 



♦The idea being- to have the string behind which the observer stands, when 
looking towards the height, at about the level of the eye. 



PLATE 12. 




PLATE 13 





^^ H 
■ I I 

<§) ***** 

«C*| &> ^ 



\ 



- 4- 



V > > 




Tn P 



1 


|...... , . 


. c 


aia 


0> ^ a £> c 

•«0 «0 *? o 


><0 
O 


i 


* ^ 6 to ; g 5 






* » » • *• 1 




*t3 


S3 £> O t3 p 





•*& 



Field Works. 51 

.instance. When completed, the profile is up-ended and nailed to 
the pickets. (PL 12, Fig. 1.) If strips cannot be obtained, the 
entire profile, except the uprights, may be made of twine. The 
profiles at the angles of the works, known as oblique or angle pro- 
files, will evidently differ from the others in length, while their 
height, on level ground, remains the same. The position of any 
point of the angle profile, as, for example, the exterior crest, is 
fixed by finding the intersection of the prolonged exterior crest 
lines of the face profiles. This result is accomplished by standing 
on the farther side of the second profile from the angle and lin- 
ing in an assistant who holds a rod vertically at the angle, one end 
of the rod resting on the ground. After the profiles are in place, 
twine should be stretched between them to indicate the various 
crest lines. The outer edge of the battens marks the extent of 
the fill, except in the case of the interior slope, which is marked by 
the inner edge when the slope is to be revetted. 

95.— Calculation of Dimensions of Earthworks. Tlie Com- 
mand of the proposed work having been fixed by the requirements 
of defilade, and the thickness by the character of fire expected, 
it becomes necessary to calculate the dimensions of the excavations, 
so that they mil furnish enough, and no more, earth than is required. 
The size of embankments and trench are, by the nature of the 
problem, fixed, as is the depth of ditch; hence the only variable is 
width of ditch, which is found as follows: 

Assuming the relief to be constant and the profile, for example, 
to be as shown in PL 13, make a sectional sketch of the proposed 
work at any point except an angle. Calculate the sectional area 
of parapet, glacis, and trench, in square feet, and from the sum of 
the first two subtract the last: the remainder divided by the as- 
sumed depth of ditch, in feet, will give the mean width of ditch, 
from which, knowing the slope of escarp and counterscarp, 
the width at top and bottom can readily be found. 

96.— Earth in embankment occupies, for a time, about one- 
twelfth more space than it did originally if untamped, but this in- 
crease is not usually taken into account in the computations for 
ascertaining the width of ditch. If the earth is tamped it occupies 
about 1-10 less space. When the relief of a work is not constant, 
it is evident that, in order to get the proper amount of earth, 



52 Field Works. 

either the depth or the width of ditch must vary. On account of 
the labor required in raising earth, the limit of depth is taken at 
8 ft.; for a similar reason, the maximum height of parapet is 
taken at 12 ft. Whatever the depth of ditch assumed, it is always 
constant. The required width at any point is found by means of 
a section of the work, as already explained, a section near the 
extremities of each face determining the width of ditch for that 
entire face. 

97. — An excess of earth will occur at the salients and a defi- 
ciency at the reentrants, although this may be partially obviated 
by making the shovelers throw toward the reentrants. 

98. — Drainage of the trench must be provided for at the time 
the work is constructed. If the fall is toward the gorge, an open 
drain will suffice; but if in any other direction, a covered drain 
(PL 50) should be left to carry the water to the ditch. 

Construction of Field Works. The details of construction and 
dimensions of earthworks will change with varying requirements 
and soil, but there are certain general principles that should be 
followed in all. 

99.— As to profile: The Normal (PL 14, Fig. 2) fulfills the 
conditions as to simplicity, protection against field artillery (in 
most soils), command of the ground in front, and cover standing, 
in the trench. The trench is stepped and steps revetted to facili- 
tate mounting the banquette, while the berm is omitted to deprive 
the assailants of a foothold. The command may be increased 
either with or without constant relief, the parapet thickened or 
reduced, and the trench made into a casemate without changing 
the type of this profile. 

100. — As to garrison: For ordinary field works, the garri- 
son is usually computed at 2 men per yard of interior crest; but 
for isolated works, this estimate should be increased by one-half. 
Embrasures and gun-banks each reduce the interior crest line 
available for troops, by 5 yards. 

101. — As to laying out tasks: Cutting lines must be marked 
by tape or pick, computations made, and the exact size of the task 
for each relief determined in accordance with the rules given in 
Chapter VIII. 

As an example of laving out tasks, assume that an earthwork 



PLATE 14. 



Ssrivmafo tier- iOOft.4^ \C$m<o/ic£ (ctiMcuti <^):Jf1U.puJlL \ 



*T"oo /-JET 



T m$- C % &i 



/"Relief. 2'Hbuef. 3'ftEusp. 



-zo a 



.CLQ d. 



Spades 7\ C J<* Shovels^ I'flei. 27?el 



y/?ei 



D/tch / 
Trench { 



.20. 

'. 2d-~ 



..20. 
'. 20- 



:??.: 



85 : 



~<95'& ~M~- 



, 6o--\---63--.\.--33---\--40- 
d ' diggers . S » a~hove/er s. 



Section 




Trench 



Figure 1. 

NORMAL PROFILE 
SHOWING TASKS. 

JPara/jet 




Ditch 




PLATE 15. 




FIG. 1 




C 



^ 



^ 



FIG/2, 



4500 to 3000 yards -f^ ^s ^*\ 
* / \ 



SL 






~\ 



r 



j|L 



Field Works. 55 

with normal profile and constant command of G ft. is to be made 
on a level site. 

Before work is commenced, the outer and the cutting lines of 
ditch and trench must be marked. As fatigue parties cannot be 
expected to excavate earth and at the same time preserve the 
proper slopes, the usual method followed is to dig vertically as in- 
dicated by the cutting lines and afterward form the slopes by cut- 
ting off the steps. 

The cutting lines for the task of the 1st Relief would be made 
on the ground, as indicated in section and plan. (PL 14, Fig. 1.) 
The 1st Relief having finished, cutting lines for task of 2d Relief 
would then be marked out; and finally, the 3d Relief would com- 
plete the slopes of ditch and parapet, and finish any w^ork not com- 
pleted by the other reliefs. 

When not practicable to revet the banquette and trench steps, 
the risers may be sloped back at about six on one. 

When necessary to throw earth more than 12 ft. horizontally, 
extra shovelers should be provided at the rate of 1 to each 2, or 2 
to each 3 diggers, depending upon the soil and the distance it is to 
be thrown. 

102.— Gun-banks, when made, are usually placed in the sali- 
ents, for the reasons that the guns will have a greater field of 
fire and it is at this point that the earth of which they are made is 
in excess. PL 12, Fig. 2 shows a gun-bank on a straight line of 
parapet, and Fig. 3 one at a salient. The top is horizontal and 3.5 
ft. below the interior crest: this distance may vary, however, for 
different pieces. All slopes are one on one, except the ramp, or 
roadway leading up to the bank; this may be as steep as one on 
four, but a gentler slope is better. The width of ramp should be 8 
ft. The level surface of the bank extends back 24 ft. from the para- 
pet and a log or fascine is half sunken and picketed near the front, 
for a hurter. The width of bank for a single gun is 15 ft. At a sali- 
ent (PL 12, Figs. 3 and 4) the angle is filled in by a straight revet 
ment from 6 ft. to 15 ft. long and the superior slope reduced to cor- 
respond to lines joining its extremities with the exterior crest 
salient. This forms what is known as a "pan coupe"." 

103.— Embrasures for field guns would be used in positions 
where the fire is required to be in one direction only; for example, 



56 Field Works. 

to sweep a road, bridge, or ford; or in the flank of a work to 
cover ground in front of an adjacent work. 

PI. 15, Fig. 1, shows the horizontal projection and the section of 
an embrasure. It is made at the same time as the parapet, by 
making the sole "s" parallel to the superior slope. The cheeks, 
"c, c," are vertical at the throat, "e," and have a slope of one on 
one at the other extremity; their height should never exceed 4 ft. 

The usual method of forming an embrasure is to stretch a string 
along the line of fire; at the throat lay off 1 ft. on each side of it, 
and at a distance of 5 ft. from the throat lay off 1.5 ft. in a similar 
manner. Right lines joining the corresponding points so deter- 
mined will mark the outer lines of the sole, which will splay one 
on ten. Each throat gabion is vertical, the extreme ones being in- 
clined three on one; the slope of the intermediate ones is secured 
by alignment top and bottom on the extreme ones. Each gabion 
is anchored independently of the others, so that one may be torn 
out without seriously injuring the embrasure. 

104. — By the Merlon is meant that portion of the parapet be- 
tween two embrasures and above the soles. Embrasures should, 
as a rule, never be closer together than 15 ft.; otherwise the merlon 
is too much weakened. 



PLATE 16. 




Fig.l 




F'g-/2 




Fio.3. 



D >a<-0" •"CF--0--Q" v -D- :i '-a_ 



-*%" 









5' 


#' 


5' 


5* 



5' 



6' 



a 

9 



-5 1 // 











Fig.4 



£' 



4' ■*' -#' *' *' 



M§. 



CHAPTER VIII.— Working Parties. 

Occasion may arise, as, for example, at night, in the presence of 
an enemy or even with a large working party, when a well-estab- 
lished system of taking and Handling tools, distributing and reliev 
ing working parties, etc., will be a paramount importance. 

105. — Organization of Working Parties. The nature of the 
required work having been decided upon, the estimate of and the 
application for the requisite number of men and tools devolves 
upon the officer charged with its execution. 

A working party of the requisite strength (which should include 
a reserve of l-10th) should be furnished, as far as possible, from a 
complete organization, a company, a battalion or brigade, and not 
from detachments of different organizations. 

106. — Responsibility. The party should be divided into re- 
liefs and the task each is to accomplish made plain before it begins 
work. The officers and non-commissioned officers of the working 
party are responsible for the amount of work done. 

107. — Taking Tools. The first relief, having been formed 
in single rank with rifles slung across the back, is marched to the 
park where the tools have previously been laid out, either in rows 
(PI. 16, Fig. 1) or in heaps. (Fig. 2.) The relief in the former case 
is advanced in line to the row and each takes a pick in the left 
and a spade in the right hand; in the latter case the party in col- 
umn of files is marched between the piles, each in turn receiving 
a pick in the left and a spade in the right hand. The relief is 
then marched in column of fours or twos to the point where the 
work is to begin. 

108. — Carrying Tools. In carrying picks and spades the 
handles are grasped near the iron, which is held vertically, the 
arms extended and the hands close to the side. In turning, the 
point of the pick should be lowered and the blade of the shovel 
raised, and when marching, either in line or in column, the han- 
dles should be splayed outward, in order to prevent interference. 
The necessity under certain circumstances of preserving silence 
makes the above precautions important at all times as a matter of 
training. 



Working Parties. 59 

109. — Extending the Working Party. When the first re- 
lief approaches the designated point it is halted, then broken ir»- 
to column of files and direction changed, if necessary, so that the 
head of the column approaches in a direction parallel to and about 
3 yds. in rear of the tape marking the front edge of proposed exca- 
vation. (Fig. 3.) When the leading file is opposite his place the 
command is given: 

(1) On right (or left) into line at tivo paces interval. (2) March. 
(3) Detachment. (4) Halt. 

The command "Halt" is given when the leading file is 1 yd. in 
rear of the tape. While the line is forming, the correct positions 
are at once taken, as follows: 

Each man on arriving at the line extends his arms horizontally, 
holding them thus until his own position and'that of the man fol- 
lowing him are established by touching hands. As soon as each 
man has his position he drives his pick into the ground on the left 
of his own task and lays his shovel on the ground, parallel to and 
at a distance in the rear of the tape equal to the width of his task 
from front to rear. 

Rifles are then unslung, belts and canteens removed, and all 
having been placed on the ground three paces directly to the rear 
of task, butts of rifles toward the front, the men sit or lie down be- 
hind their shovels until the order "Commence work." 

110.— Extension of 2d and 3d Reliefs. Each man of the 1st 
relief, after completing his task, scrapes his tools and lays them 
together in rear of the trench. 

The task being completed, each man secures his accoutrements 
and rifle, and then, under direction of his officers, closes in to the 
left (or right), forming column of fours, which is then marched 
back to camp. 

As an incentive to rapid work, each relief should be allowed to 
return to camp on the completion of its task. 

If the working party be large and the work of a complicated 
nature, each relief should arrive in successive detachments and 
their location on the work should have been previously designated, 
so that there need be no delay or confusion, even at night. 

Work should not be commenced until the distribution of the 
entire relief is complete, since any change after work has begun 
tends to confusion, loss of tools, and delay. 



60 Working Parties. 

111.— Tasks. An untrained workman can excavate in ordi- 
nary soil one cubic yard of earth per hour for four consecutive 
hours. As some men work slower than others, however, it is 
usual to estimate at 6 hours per man for the lifting of 4 cu. yds. 
of earth from a trench 3.5 to 5 ft. deep and throwing the same a 
horizontal distance of 10 ft. 

When it is necessary to throw the earth more than 12 ft. hori- 
zontally, extra shovelers should be provided for rehandling it, in 
the proportion of 1 shoveler to every 2 diggers. 

When exposed to the enemy's fire, a skirmish line is kept well 
to the front and the earth first excavated is thrown close to the 
edge of the ditch, forming a screen which is gradually thickened; 
under other circumstances the earth first excavated is thrown 
farthest. 

Five feet, or two paces, is the usual distance apart for men to 
work, but they may be posted as close together as 4 ft., while using 
the heavy pick and shovel. As a precaution against injury to ad- 
jacent workers, the men should swing the pick in a direction per- 
pendicular to the tape. 

112.— Working parties may be extended at less or greater in- 
tervals by making the corresponding changes in the commands: 
when this is done, it will usually be necessary to verify intervals. 

When necessary to complete a task in the shortest possible time, 
or when the men available greatly exceed the number of tools, 
working parties should be formed in double rank, two men being 
assigned to each set of tools, which should be carried by the front 
rank man. W'hen working in this manner with a double relief, 
the men, under direction of non-commissioned officers, should 
change off every 10 or 15 minutes. 

Officers having general supervision of the work should not be 
changed at the same time the reliefs are. 

The sizes of tasks based on the 4 yd. rule may be arranged as 
shown in diagram. (Fig. 4.) For arrangement of tasks in difficult 
soil, see PL 14. 



CHAPTER IX.— Revetting Materials and 
Revetments. 

113.- A Revetment is a facing used to bold up an embank- 
ment at a steeper slope than it wo aid assume naturally. 

114.— Revetting Materials. The revetments most commonly- 
used in field engineering are made either of brushwood in the 
rough, fascines, gabions, hurdles, planks, timber, sods, sand-bags, 
pisa, adobe, bamboo, or of a combination of two or more of these. 

115.— Brushwood, which is used in making the first four, 
should be of willow, birch, ash, hickory, or hazel, and is most pli- 
ant when not in leaf: it may be of any size when used in the rough, 
but should not exceed an inch in butt diameter for gabions and 
hurdles and 2.5 in. for fascines and pickets. 

The working party cuts and binds the brushwood in bundles 
of about 40 lbs. each, putting the large and small in separate piles 
with butts in the same direction. For convenience, the detail 
should be divided into three parts— one for cutting, one for sort- 
ing and binding, the other for carrying and, if necessary, loading. 
Tools required and time necessary are as in "Clearing the Ground" 
(Chap. V.). 

116.— Withes (PL 17, Fig. 1), which are used for binding and 
sewing, are made by twisting pliant rods. The butt is held under 
the left foot and the twisting commenced at the small end, care 
being taken to avoid breaking or kinking the rod. The pliancy of 
the rod may be increased by heating it. In using the withes for 
binding, an eye is made at the small end, then the withe is passed 
round the bundle, the butt passed through the eye and twisted 
until a kink is formed, when the butt is thrust (buried) in the 
bundle. 

117.— Fascines. A fascine is a bundle of rods tightly bound 
together. It has a length of 18 ft., a diameter of 9 in., and weighs 
about 140 lbs. 

Fascine Rack. The fascine is made in a cradle rack of five 
equidistant trestles (Figs. 2 and 4), the outer ones being 1G ft. 
apart; the crotches are each 2.5 ft. above the ground and aligned. 
The stakes for the trestles should be from 2.5 to 4 in. in diameter 



PLATE 17 




Revetting Materials and Revetments. 63 

and from 5 to G ft. in length. Those for the outer trestles are first 
driven and securely bound together with wire or rope, then a line 
is stretched from crotch to crotch and the interior trestles made 
in a similar manner; the stakes should be driven firmly into the 
ground and each should have a length of 2 ft. above the crotch. 

Fascine Choker. For the purpose of gauging the circum- 
ference of the fascine and for cramping it in binding, the fascine 
choker (Fig. 3) is used. It consists of two stout bars or hand- 
spikes, 4 ft. long, to each of which is attached a collar 18 in. from 
the end, the collars being connected by a stout chain, to which 
are attached two gauge links 28 in. apart. The choker is used by 
a man on each side of the rack taking a bar of it and resting the 
short end on top of the fascine, chain being underneath (Fig. 4, 
"a"); then each passes his bar over to the other (the short ends 
passing around and under the fascine), and each bears down on 
the end of his lever. (Fig. 4, "b.") 

Making the Fascine. The trestles having been prepared, 
the fascine is made by laying brushwood, trimmed if practicable, 
in them, the pieces breaking joints and crooked ones being partly 
sawed or cut through. The rods should extend from 18 in. to 2 ft. 
beyond the extreme trestles and the bunch made of uniform size 
throughout. (Fig. 4.) 

The choker should be used occasionally for testing the size, and 
when of such dimensions throughout that the gauge rings meet, 
the fascine is bound. This should be done with wire or tarred 
rope, which is passed twice round the fascine and securely fas- 
tened, the bindings being 12 in number, the two outer ones 3 in. 
outside the extreme trestles and the others at intervals of about a 
foot and a half. This allows the fascine to be cut into lengths of 
6 or of 9 ft. Five men require about an hour to make a fascine. 

118.— Gabions. Gabions are open cylinders 2 ft. in exterior 
diameter by 2 ft. 9 in. in height, varying in weight from 35 to 50 
lbs.: they are made of brushwood, strap iron, iron bands or sheet iron 
and from 9 to 14 pickets each. The interlaced brushwood in gabions 
is called the watling or web. Gabion pickets should be 3.5 ft. in 
length and from an inch to an inch and a half in diameter. The 
rods for the web should be from one-half to three-fourths of an 
inch in diameter, although smaller may be used. Wicker gabions 
-5- 



64 Revetting Materials and Revetments. 

are most easily made with the aid of a gabion form, which is a 
circular piece of board 21 iu. in diameter, with equidistant notches 
on its circumference, the number of notches depending on the size 
of the brushwood and running from 9 to 14. (Fig. 5.) 

The construction of the Wicker Gabion (Fig. 7) is as follows: 
Watling. The gabion form is laid on level ground and a 
picket driven vertically in each notch, the thick and thin ends of 
the pickets alternating. The form is then slipped up the pickets 
about a foot and held firmly in place by means of a rope, which is 
tied loosely round the pickets just below the form and then tight- 
ened by a rack stick (Fig. G), the rope holding the pickets firmly 
in the notches. The rods for the web having been stripped of 
their leaves, the web is commenced by laying the butts of two rods 
in adjacent spaces between pickets, resting on the form. The rear 
rod, passing outside the second picket, is then bent inward, pass- 
ing over the first rod, inside the third picket, and then out. (Fig. 
5.) The other rod, which is now the rear one, is similarly treated 
and the watling continued by using the rods alternately. This 
method of watling is called pairing. On coming to the end of a 
rod a fresh one is laid alongside and woven with it for a short dis- 
tance. The web is continued to within 3 in. of the ends of the 
pickets, care being taken to keep the pickets vertical and to make 
the web close by frequent use of the mallet. 

Sewing. To prevent the web from coming off the pickets it 
is then sewed with wire, heavy twine, or withes, in four places, as 
follows: Take an end of a withe in each hand, the middle of it 
resting on top of the web, pass the ends of it through the web about 
6 in. down the sides, one from without inward and the other from 
within outward; pull taut by bearing downward. Pass the ends 
through the web again (> in. farther down and tighten as before. 
Proceed in the same manner a third time and then bury the ends 
of the withe in the web. The sewing should be at equal inter- 
vals and the two ends of the withe, when pushed through the 
web, should be separated by two or three of the watling rods; wire 
is much easier worked and more durable than withes. The partly 
completed gabion is now inverted, the form removed, and the wat- 
ling continued as before, until the gabion has a height of 2 ft. 9 in., 
when it is completed by again sewing as before explained. The 
ends of the pickets that were driven into the ground are now 



Revetting Materials and Revetments. 65 

trimmed to within 3 in. of the web and sharpened, the opposite 
ends sawed off to within an inch of the web, and a carrying picket 
driven through the sides of the gabion perpendicular to the axis 
and a few inches from it. 

Three men should make a gabion in an hour. 

119.— Wicker Gabion Without the Gabion Form. Where 
the form is not at hand, the wicker gabion is made by first 
describing on the ground a circle with a 10.5 in. radius and then 
driving the pickets at equidistant intervals on this line. The 
watling is commenced at the ground and run up to the full height, 
care being taken by frequent gauging to keep the dimensions 
accurate. It will be necesary for one man to devote his entire 
attention to keeping the pickets in position, while a second makes 
the web, and a third prepares the rods. Three men should 
make a gabion, without the form, in an hour and a half to two 
hours. Instead of sewing, the gabion may be finished by driving 
four forked pickets (Fig. 8) in the web alongside of the gabion 
pickets. 

120.— The Hoop or Strap Iron Gabion. This is more dura- 
ble and more quickly made than the wicker gabion, but is 
heavy, weighing 55 lbs., and liable to splinter dangerously. The 
form for this gabion is used solely for gauging and shaping the 
bands. 

To make the hoops, describe on a wooden platform a circle 
with a 1 ft. radius and divide it into 6 equal parts. Make auger 
holes at points of division and insert in them wooden pins about 
5 in. long and triangular in cross section, the bases of the tri- 
angles being on the interior of the circle. (Fig. 9.) Wrap the 
strap iron once tightly round the pins, thus forming an hexagonal 
hoop. Mark the point where the hoop is to be joined, then remove, 
punch, and rivet it. As the iron is usually 1 in. wide, the com- 
pleted gabion will require 33 of these hoops. 

To make the gabion, place a hoop on the ground and an- 
other on it in the positions shown. (F.'g. 10.) Drive a picket 
vertically in each of the triangular spaces, then place the remain- 
ing hoops alternately over the first and second. Drive nails in 
four of the pickets outside the extreme hoopi to keep the gabion 
intact. 

121.— The Sheet Iron Gabion. This gabion is made of a piece 



66 Revetting Materials and Revetments. 

of sheet iron 2 ft. 9 in. x 6 ft. 4 in,, riveted or wired together along 
its shorter edges. 

122.— Hurdler. the hurdle is a brushwood mat 2 ft. 9 in. 
Wide by 6 ft. long, the length corresponding very nearly to the 
'circumference of the gabion. An even number of pickets, usually 
10, is used in making it, the extreme pickets being somewhat 
heavier than the interior ones. (Fig. 11.) 

Construction of Hurdles. Describe on the ground an arc 
with an 8 ft. radius, measure off 6 ft. of this arc and drive 10 
gabion pickets along it at intervals of 8 in. (Fig. 11.) Commence 
the watling in the center space on the ground by randing— i. e.,. 
working with a single rod alternately inside and outside of the 
pickets; on reaching the end picket the rod should be twisted as 
a withe, so as to avoid breaking it, and then returned toward the 
center in the same manner as at first. When approaching the 
end of a rod another should be laid alongside of and randed with 
it for a distance of two or three pickets. Pairing, as in gabions,, 
should be resorted to in finishing the top and bottom of the web, 
and the hurdle should then be sewed as described for the gabion. 
When the rods used in watling are very small the process of slew- 
ing should be resorted to: this is the same as randing with the 
exception that 2 or 3 rods are laid alongside each other instead of 
using them singly. Slewing makes weaker work than randing. 
Three men should make a hurdle in two hours; two work at the 
web and the third prepares the rods. The completed hurdle 
weighs about 50 lbs. The hurdle is made on a curve and after- 
ward flattened as much as possible, because it is found that by 
so doing it is less liable to warp than if made flat. It should be 
placed in a road or revetment with the concave side toward the 
earth. 

123.— The Continuous Hurdle is usually preferred for revet- 
ting purposes to single ones joined. It differs from the latter 
in that the pickets are driven at once, at intervals of 12 to 18 in. 
according to their thickness, in the position the revetment is to 
occupy, but at a slightly gentler slope, so as to allow for straight- 
ening when the earth is tamped. It is constructed by randing or 
slewing, two men being assigned a task of 10 or 12 ft. in length, 
which they should finish to a height of 4 ft. and anchor, in from 
one-half to three-quarters of an hour. 



PLATE 18. 



Revetments. 





68 Revetting Materials and Revetments. 

124.— Planks, when used for revetting, should be placed 
edgewise and held in position by stout stakes, which should be 
anchored. They make a neat, durable and quickly made revet- 
ment. 

125.— Round timber from 3 to 8 in. in diameter may be used 
in the same manner as planks, but the revetment is more difficult 
of construction and is not so durable. 

126.— Sod for revetting purposes is cut of a uniform size— 18 
in. long, 9 in. wide, and 4 in. thick. They should be laid in alter- 
nate rows of headers and stretchers, grass down, breaking joints, 
and perpendicular to the slope. The top layer should be all head- 
ers and have the grass up; alternate rows should be pinned secure- 
ly, using split pickets, if possible, as with them there is less liabil- 
ity of splitting the sod than when round ones are used. Two men 
should lay from 70 to 100 sods per hour, depending upon whether 
or not pickets are used. 

127.— Sand-bags are made of coarse canvas or bagging 
material, and, when empty, measure 2 ft. 8 in. by 1 ft. 4 in. When 
filled they are supposed to contain 1 cubic ft. of earth; it is found 
in practice, however, that a cubic yard will fill from 48 to 50, mak- 
ing their average size 1 ft. 6 in. long, 10 in. wide, and 6 in. thick. 
Each bag has eyelet holes near the mouth through which a stout 
cord passes, to expedite tying, when filled. 

For filling sand-bags the working party is divided into squads 
of 6: 2 with shovels, 1 with a pick, 1 to hold the bag, and 2 to tie. 

Each squad fills 150 bags per hour. This task may be consid- 
erably increased, however, in easy soil or with trained men, and 
the rapidity of the work more than doubled by having a double 
relief and keeping the men constantly changing. 

128.— Revetments. Brushwood Revetment is made by driv- 
ing pickets at intervals of about 12 in. along the foot of the 
proposed slope. The top of the pickets when driven should be 
as high as the proposed revetment, and the pickets should be 
anchored by wire to logs or stout stakes in the parapet. Loose 
brushwood is laid closely behind the stakes and earth tamped 
against it, the construction of the parapet going on at the same 
time. 

Brushwood revetment is rapidly made in daylight, but is neither 
durable nor sightly. 



Revetting Materials and Revetments. 69 

129.— The Fascine Revetment. (PI. 18, Fig. 1.) This is 
made by laying the fascines in single rows of stretchers, breaking 
joints, each fascine being pinned to the parapet by 5 or 6 pickets, 
and every second or third row securely anchored. 

Six-foot fascines should be used occasionally as headers. The 
bottom fascine is sunk about one-third of its diameter by excavat- 
ing a shallow trench. The construction of parapet and revetment 
proceed simultaneously. Slope should not be greater than four 
on one. The defects of this revetment are the weight of the fas- 
cines, the large quantity of brushwood required, and the fact that 
the fascines are held in place by anchors and pickets in the eartb 
which they support. 

130.— The Gabion Revetment. (Fig. 2.) This is made by 
first sinking a row of fascines about 3 in. at the foot of the slope, 
so as to give an inclination of four on one to the gabions resting 
partially on them. Earth is tamped behind and in the gabions, 
and sod or sand-bags placed on top. Where greater height is 
required two rows of gabions may be used with two fascines, well 
picketed, between them. 

Gabions make one of the strongest and most durable revet- 
ments, their own weight when filled being usually sufficient to 
retain the embankment. 

131.— Hurdles. These make a poor revetment unless the 
method is followed of constructing a "continuous hurdle" at the 
same time with the parapet. To do this, the pickets are driven 
along the foot of the slope at an inclination of about three on one, 
when the final slope is to be four on one. The watling is made 
continuous by randing or slewing, each two men having four 
paces of hurdle as a task, and taking care to work in their rods 
with those of adjacent sections. (Fig. 3.) 

132.— Plank or Timber Revetment. (Fig. 4.) This is made 
by driving heavy stakes into the ground at the proper angle, plac- 
ing the planks or timbers behind them, then filling in and tamp- 
ing firmly. The stakes must be anchored. This revetment is 
neat and durable. 

133.— Sod Revetment. (Fig. 5.) This is made by laying the 
sod in alternate layers of headers and stretchers, grassy side down, 
breaking joints and perpendicular to the face of the revetment. 



70 Revetting Materials and Revetments. 

Each sod should be well settled before another is placed on it and 
the top layer should be headers with grass up. It is well to 
pin alternate rows by means of split pickets, three-fourths of an 
inch in diameter and 9 in. long. This revetment is made of uni- 
form thickness throughout by using double rows of stretchers. 
If the grass is long it should be mowed. If the sod is very wet 
when laid the revetment will crack in drying. Two men well 
supplied with sod should lay two paces of revetment, four and 
one-third feet high, in an hour. 

This revetment has the advantage of not splintering like 
gabions, fascines and boards, but should not be used when other 
material is obtainable, because ordinarily it will not stand long 
at a steep slope (three on one being about the limit), cannot be 
used when very dry or frozen, and requires great care to build 
properly. 

134.— Sand-bag Revetment. (Fig. 6.) This is made by lay- 
ing alternate rows of headers and stretchers, breaking joints, and 
perpendicular to slope, seams of stretchers and chokes of headers 
being put in the embankment. Men working in pairs lay the 
bags, settling them firmly in place with a mallet or spade. This 
revetment is not very durable, but the bags are easily transported, 
may be used with any soil, and are invaluable in making hasty 
repairs and loop-holes. 

135.— A very durable revetment (Fig. 7), much used in the 
defenses of Washington, 1861-5, was made of posts (oak, chestnut, 
or cedar) cut in lengths of 5.5 ft. and placed side by side, at a slope 
of six on one. The footing was a 2 in. plank laid in a trench exca- 
vated for the purpose. The tops of the posts were sawed off 16 
in. below the interior crest and capped by a half-round timber, 
all being securely anchored in the parapet. Crowning was com- 
pleted to the requisite height with sod. 

All revetments that are liable to splinter should be crowned to 
a height of at least 8 in. with sods, sand-bags or earth. 

136.— Pisa Revetment is made of earth and clay, to which 
has been added enough water to reduce the mixture to a working 
consistency. A trench 6 in. deep and 18 in. wide is first dug, its 
nearest edge marking the foot of the revetment. Pickets, of 
sufficient length to reach the top of the proposed revetment, are 



Revetting Materials and Revetments. 



71 



firmly driven, at the proper angle, about 2 in. from the near edge 
of the trench, at intervals of about a yard, and then anchored. 
Boards placed on edge are now laid against the pickets on 
the trench side. The trench is then filled with the mixture, 
tamped, and more added, other boards being placed on top of the 
first, as required, and the mixture forced closely against them. 
The construction of the parapet goes on at the same time with 
the revetment. When completed, the pickets and boards are 
removed. This revetment is neat and durable, but cannot be 
rapidly made. 

137. — Adobe Revetment. The adobe is a sun-dried brick, 
about IS in. x 9 in. x 4.5 in., and when carefully laid with the same 
bond as given for sod or sand-bag, forms a neat and very durable 
revetment, exceeding in the latter respect any of the other varieties 
mentioned. 

137a. — Bamboo Revetment. Where material is available green 
bamboo split into strips an inch and a half wide makes an excel- 
lent revetment. It is constructed by randing in the same manner 
as the "continuous hurdle," care being taken to have the adjacent 
strips break joints. 

The following table shows amount of various materials re- 
quired for 100 running feet of 4 ft. 4 in. high revetment: 



Kind of Revetment 


Fascines 


Gabions 


Sod 


Sand-bags 


Pickets 


Fascines 

Gabion 

Sod 

Sand-bag 


30 
6 


50 


267 

400 

1867 


867 


150 
1000 



PLATE 19. 



Field Casemates. 




Fig. 3, Casemate #75jE 

mlh banquette 




Rg.4. Casemate jconstmcted 
same time as parapet. 




Fig. 5. 
Qp#/2 Meld Casemate. 




Casemate behind Wall. 

i 




Fio. 7. 



-aial 



CHAPTER X.— Field Casemates and Magazines. 

138.— In all field works, protection against both weather and 
hostile fire must be provided for the garrison. 

These shelters are constructed by building a chamber of wood 
sufficiently strong to bear the necessary earth covering, and by 
protecting this in front by an embankment thick enough to with- 
stand direct artillery fire. 

Two general forms are used: 

(1) Those which, after providing complete protection from 
direct fire, have their roofs sloped to the rear at an angle greater 
than the angle of descent of the enemy's projectiles, generally 
about one on four; and 

(2) Those which have horizontal roofs, the earth covering being 
so high and massive as to protect against artillery fire by its thick- 
ness alone. 

The first class is preferable, the work of construction being very 
much less than in the second class, as the embankment is not so 
high and the earth on the roof does not require to be thicker than 
16 in., as it has to resist only the dropping fire of small-arms and 
the fragments from bursting shrapnel. Moreover, it gives much 
easier drainage to the ditch in rear. 

139.— The construction of the timber part of the casemate is 
practically the same in both cases. The vertical timbers being 
rough tree trunks, about 1 ft. in diameter, placed at intervals of 
3 or 4 ft., and strutted when necessary. The roof timbers in sim- 
ple casemates being not less than 8 in. in diameter and the inter- 
stices filled with small poles or brush. In case the protection has 
to be proof against vertical fire of mortars, the earth mask on the 
roof must be 6 ft. in thickness and a correspondingly stronger 
timber construction must be provided: these are shown in PI. 19, 
Figs. 1 to 7. 

In calculating floor space, each man should have from 9 to 18 
sq. ft.: the former when crowded, the latter when not. 

139a. — The following is a bomb-proof construction which would 
be safe under the fire of projectiles having a bursting charga of 
9.9 pounds of explosive gelatine and a penetration of 5 feet before 
bursting: 



74 Field Casemates and Magazvnes. 

1. Frames of 8-by-8-inch pine, 5.5 feet high and 6.5 feet wide 
in the clear, with upper corners braced, spaced 10 inches apart. 

2. Sides of poles or boards outside the frames. 

3. On top: (a) a longitudinal layer of double thickness of rail- 
road iron or a double thickness of 4-by-6-inch timbers; (b) cross 
layer of fascines; (c) longitudinal layer of 8-by-8-inch oak; (d) 9 
feet of earth; (ej 20 feet of earth on exposed side. 

140.— Magazines are of two kinds: First, those intended to 
hold the temporary supply for guns or troops when in action; and, 
Second, those intended for the purpose of storing ammunition iu 
large quantities. 

The first variety consists of recesses in the interior slope of the 
epaulement— barrels or gabions are excellent and when not obtain- 
able may be replaced by empty ammunition boxes placed in holes 
excavated for their reception. 

Magazines of the second class are used only in works of great 
defensive value and then only when ample time is available. 
They are made in the same general manner as the casemates 
heretofore described, except that great care must be taken to 
render the structure as dry as possible and to secure good venti- 
lation. 

141.— The general plan of execution of these works is as 
follows :— 

(1) Magazine shown in PI. 20, Fig. 1. 

The mask in front should be 20 ft. thick. The roof consists of 
a row of timbers or logs 8 in. in diameter, overlaid with steel rails, 
and then covered with a paulin, well tarred if possible. On this 
is placed 16 to 18 in. of earth. The ends are made of logs, 12 in. 
in diameter, planted in a double row, Breaking joints. The en- 
trance is at either one or both ends according to circumstances. 
The doors, 2 ft. 6 in. in width, are made of planks crossed, and are 
hung next to the front wall of trench, opening into a passage 
formed by a row of upright logs parallel to those on the end of 
the magazine. At the end of the passage farthest from the first 
door a second one is hung, opening into the magazine. The ver- 
tical timbers in front and rear of trench support a revetment of 
planks or hurdles. The floor should be raised at least 6 in. from 
the bottom of the trench to guard against dampness. Care should 
be taken to facilitate the draining of all water that falls on the 



PLATE 20. 




¥ a ^ zine t J"l M^zZ'atj Bo ^^^ zme - 




Two Storied, Block House. 




Caponier in front of wall. 

^ *y j ,1^,1 1,1, ,i ,i ,mp, 




76 Field Casemates and Magazines. 

roof, and that the trench itself is drained away from the ends of 
the magazine. 

142.— Another form is as follows:— Determine the space need- 
ed for storage of ammunition. Then build the timber work as 
in the preceding, tirst excavating to a depth of 4 or 5 ft. over 
the entire site. There will be no ends to be closed by timbers. 
The roof is made of timbers 12 in. in diameter, well supported by 
uprights of same size and long enough to give sufficient head 
room. The sides and ends should be revetted w T ith plank, if pos- 
sible, and the floor raised 6 in. above the earth. The center of 
the roof is raised a foot above the sides and surmounted by a 
layer of 6 in. of earth, well tamped; over this is laid a paulin and 
the earth mask is then placed over all to the thickness of 8 ft.; 
the covering mass in front should not be less than 20 ft. in thick- 
ness. Entrance is gained by means of a doorway opening into 
a passage which communicates through a return with the inte- 
rior of the magazine. Doors made of crossed planks are hung 
as indicated in the plan. If time is available, and the planks 
at hand, an interior chamber should be formed, leaving an air 
space around the magazine proper; and inlets may be constructed, 
care being taken that they are not situated in exposed positions 
and that their course is such as to prevent the entrance of sparks. 
The roof should be rounded off so as to afford the easiest drain- 
age. If the earth excavated is not sufficient to cover the roof, 
the necessary amount may be taken from a trench dug around the 
outside. 

This form of magazine may with advantage be placed in a 
traverse. 

143.— In case timber is not at hand, gabions and fascines may 
be used to build the magazine in the manner shown in PI. 20. 

144.— Block Houses are defensible shelters for infantry, al- 
though, under certain circumstances, they contain artillery. 

They are generally used for the purpose of flanking defenses 
whose fire cannot reach into the ditch. 

They are constructed either of upright timbers set in the ground 
close together, or horizontal timbers laid one upon the other; the 
timbers being in two rows, breaking joints in each case, or, if both 
methods are used, the outside row should be horizontal and the 



Field Casemates and Magazines. 77 

inner vertical. They should have at least G ft of head room aud 
should not be less than i) ft. wide, as this allows one row of beds 
only. The roof should be of solid construction and covered with 
earth to the thickness of 2 ft. and should project 2 ft. over the 
wall to protect from dropping fire. 

The walls should be masked with earth as high as possible and 
a ditch dug around the entire building. Loop-holes are made at 
the height of 4 ft. 4 in. and are cut according to circumstances, 
as described in Chap. XIII. If necessary, block houses may be 
sunk in the ground, but a limit of 4 ft. in depth should be observed. 
The shape will conform to the necessities of the case. 

145a. — The Spanis,h Block House is a modified form of the 
one described; it is loopholed for two or three tiers of fire, and 
as asecondary defense of especial value if attacked by artillery, 
it has shelter trenches far enough in front to escape splinters from 
the house. (See Par. 191.) 

145.— In isolated positions they are advantageously made 
cruciform, thus presenting an opportunity for flanking each face 
of the house. When in wooded and mountainous countries, 
where artillery is not to be feared, these houses may be made with 
two stories, built so that the angles of the upper story project over 
the sides of the other, forming a machicoulis gallery, thus prevent- 
ing the occupation by the enemy of the dead space in front of 
the straight walls. 

146.— Caponiers are sunken block houses placed in the ditch 
of fortified places to prevent their occupation by the enemy: they 
are loop-holed about 18 in. from the ground, so as to have the most 
effective plane of fire. (PI. 20.) 

147.— Tambours are essentially block houses, having for their 
object the protection of angles, and the flanking of sides of build- 
ings, and are especially useful in defending doors of buildings. 



CHAPTER XI.— Field Works in Combination. 

148.— Where several field works are used in conjunction, either 
as an intrenched position or in the investment of a fortress, city, 
or other important point, they constitute what is known as a Line 
of Works. 

A Line of Works may be continuous, that is, forming, together 
with natural obstacles, an unbroken line, or, with intervals, by 
which it is understood that the works are distinct, either support- 
ing each other or not, and the spaces between them not impassable 
by reason of natural obstacles. 

149. — Lines with, intervals have the following advantages over 
continuous lines, viz.:— 

(a) They involve less labor. 

(b) The garrison of the defenders may be smaller. 

(c) They allow greater freedom of movement for counter- 
attacks. 

The general principle to be followed in their construction con- 
sists in forming a line of fortified points or pivots. These points 
or pivots detain the enemy's advance, since he .would hardly pass 
them and expose his flanks and rear, while a continued unsuccess- 
ful attack on the strongly fortified pivots would open the way for a 
counter-attack by the defenders. 

When, however, the defense is intended to be solely passive, 
which would be the case while awaiting reinforcements, or when 
the enemy greatly outnumbers the defenders, the intervals would 
be obstructed by felling trees or using any available obstacles, 
since counter-attack is not contemplated. 

In the use of lines with intervals, if the general defensive line 
is straight the works could be blunted lunettes with flanks traced 
so as to protect the front of adjacent works. If on a convex curve, 
the capitals should radiate from a common center, while on a curve 
concave toward the enemy, the capitals should converge and the 
front of each work might be a straight line. 

When impracticable to construct the main works of a line with 
intervals, within supporting distance (600 yds. for infantry and 
2000 yds. for artillery)* of each other, intermediate works retired 



♦Continuous dangerous space for Springfield Magazine rifle is about 600 yds. 



Field Works in Combination. 79 

from the main line, not more than half the interval, may be 
used. 

In PI. 21, Fig. G, is shown such an arrangement, the pivots being 
single works while the artillery is retired from the main line and 
supported by infantry in shelter trenches. 

Where the interval is as great as 1500 yds. it is advisable to 
strengthen the pivots considerably, forming groups, the individ- 
ual works of each group being so traced as to afford mutual de- 
fense. (PL 15, Fig. 2.) Each group in this latter arrangement 
forms a strongly fortified point of support and would usually have 
sufficient strength in itself to resist assault. 

150.— Sometimes, when the defense of a line is of vital import- 
ance to the defenders, a double line of works is employed, the front 
line being shelter trenches or open field works of slight profile, 
the second line, not over 500 yds. in rear of the first, being field 
works of strong profile. 

151.— Artillery should, as a rule, be placed outside of and some- 
what retired from the works and protected by their own gun-pits 
or epaulements, for the reasons— 

(1) That the works gain much in simplicity and rapidity of 
construction. 

(2) That this disposition draws the enemy's artillery fire from 
the works and renders it more scattering. 

(3) Greater mobility is given to the defender's artillery in case 
of advance or retreat. 

(4) A better tactical position for this arm can often be secured 
than the one selected for infantry. 

152.— As examples of continuous lines, PL 21, Fig. 1, is known 
as the redan trace with curtains. Fig. 2 is a modification of Fig. 
1, the redans being blunted. Fig. 3 is the tenaille trace. Fig. 4 
is a tenaille and redan trace. The cremaillere trace (Fig. 5) has 
long faces and short flanks. 

With respect to the continuous lines above mentioned, the 
preference on a level site would usually be given to the trace shown 
in Figs. 1 and 2, the artillery being placed in the most favorable 
position along the curtains, with machine guns in the most im- 
portant redans. 

The tenaille and the tenaille and redan trace (Figs. 3 and 4) 
-6- 



PLATE 21. 



FIG!. 

450 to 600 yards /V*&>*> >»»* 

FIG.2. 



ISO to eOQutoek / — g»»«>5«n»fr 

FIG.5. 




cr^ 



600 to iZOO yards 



6oo to 



FIG. 7. 




Field Works in Combination. 81 

are objectionable, in that they involve more labor, cannot bring as 
direct a tire to the front, and the faces are liable to enfilade when 
the salient angles approach 90°, while on the other hand, if a 
salient, as "S," Fig. 4, approaches 120°, mutual defense of the 
faces, "f" and "g," would be lacking, thus making the redan, "R," 
necessary. This trace may, however, be rendered unavoidable by 
the conformation of the ground. 

The cremaillere trace finds special application in a position such 
as is indicated in Fig. 5, viz., joining two points, one at the top and 
the other at the bottom of a slope, the short flanks affording but 
limited opportunity for enfilade fire. 

153.— The strength of a defensive position lies in a great 
measure in the proper utilization of the accidents of the ground; 
thus, the traces that have been mentioned may have to undergo 
considerable modification to be appropriate to the varieties of 
terrain constantly met. It is evident that, in a broken or hilly 
country, one by preference would occupy the heights. These, from 
a tactical point of view, possess the advantage of overlooking 
the low ground in front, besides the great advantage of conceal- 
ing from the enemy the movements of our own troops in rear; but, 
since all else must be subordinated to fire effect, it is evident that 
such a line on the heights should be selected that the defenders 
may completely cover the ground over which the enemy must 
approach. This naturally leads to the inquiry as to how that line 
may be determined. 

Heights, great or small, usually present the profile shown 
in Fig. 7, that is to say, they have a steepest slope, "b c," which 
is joined to the crest and to the valley below by the two gentler 
slopes, "a b" and "c d." In order, then, to heat the zone "b c" it 
is necessary to occupy the crest "c" or some point below it on this 
slope. To distinguish this crest from others, it will be called the 
military crest. 

With the inclination of this steepest slope greater than one on 
four, it is unusual to construct anything but shelter trenches 
along the military crest, the artillery being retired sufficiently and 
placed in such positions as to command a good view of the rest of 
the field. With gentler slopes, however, the artillery may be 
placed at intervals along the military crest, the intermediate spaces 
being held by infantry in shelter trenches. 



82 Field Works in Combination. 

A better disposition than this, where the ground permits of it, 
is to place the infantry trenches part way down the slope in front 
of the military crest, the artillery occupying a position in rear of 
and close to the crest, so that little more than the muzzles of the 
pieces are visible. In this case, care must be taken that the infant- 
ry trenches do not mask the fire of the artillery. 

In choosing a defensive position the ground should be viewed 
from the highest point in the vicinity, and by frequent practice the 
eye so trained that the military crest is at once apparent and the 
slopes instinctively classified with respect to their use by the 
different arms. 

Finally, the distance to a number of visible permanent points 
in front of the works should be determined and recorded, so that 
there may be no necessity for range finding during the enemy's 
advance. 



PLATE 22. 



B-ur.1 





«*# Fig.S. 



<% s* ** * r 

r,,|j /iijjr 




Fig.3. 




Mff,4. 




i 




^^ 



CHAPTER XII.— Siege Works. 

154.— When it becomes necessary to besiege a place, it may be 
approached by common trench work or by some form of sapping. 
As the common trench and the flying sap are the work of infantry, 
they alone will be referred to. 

155.— The method of providing the working party with tools, 
laying out the work, and extending the working party is described 
in Chap. VIII. It is to be noted, however, in work of this char- 
acter, that token extending along a zig-zag, upon reaching the angle 
the order of forming up must be reversed. Thus, if the column from 
b to c (PL 22, Fig. 1) were forming on the left, upon reaching e f, 
it would form on the right. 

156.— Common Trench Work. This may be used as a par- 
allel, an oblique approach, or communication. The work done 
by reliefs in constructing a parallel is shown in Fig. 2. In this 
case, as musketry fire must be provided for, the second relief cuts 
out the top step. Should it be necessary to revet the bottom step, 
fascines for this purpose may be carried by the second and third 
reliefs. This may be and usually is omitted until the parallel is 
completed. Fig. 3 shows the common trench used as an oblique 
approach or communication. Should the trench be found wide 
enough the task of the third relief may be omitted. 

157.— The Flying Sap (Fig. 4) is similar to common trench 
work, except that in the former case the embankment is revetted 
with gabions. 

In taking tools, each man of the first relief is, in addition to his 
pick and shovel, provided with two gabions. In laying out the 
tools, a shovel should be fastened in one gabion by being placed 
between two of the gabion pickets, handle of the shovel inside. 
A pick should be secured in the other gabion by having its point 
pushed under the pairing rods, handle inside. The gabion with 
shovel is taken in the right hand, the one with pick in the left: 
both gabions being carried by carrying pickets. 

158.— The extension in the flying sap is made from single 
rank on the right or left, and differs from the extension in com- 



Siege Works. 85 

mon trench work in that the interval, in the former case, is the 
width of two gabions. Each man, on coming into line, places 
his gabions so that they touch each other along the inner edge of 
the tape, takes out his tools and lays them down, as explained for 
working parties in Chap. VIII., and waits for the command, "Com- 
mence work." In commencing work, the gabions should first be 
filled; hence the position of each pair of gabions should be recti- 
fied before this command is given. 

159.— Each branch of a zig-zag should receive such direction 
as not to expose it to enfilade fire from any point of the defenses. 
Its prolongation should, therefore, fall outside of the most ad- 
vanced salient of the collateral works. Ordinarily it would not 
be longer than 100 yds. A parallel should be stepped in order to 
facilitate an advance from it. 

160.— A portion of the parallels and approaches used in the 
capture of Fort Wagner, Morris Island, S. C, September 7th, 1863, 
is show r n in PL 23. 



PLATE 23. 




TLATE 24. 



Figure 1. 



Figure 6. 




CHAPTER XIII.— Defense of Localities. 

161. —Walls. Should the enemy close on them, walls must be 
so prepared that they will neither screen nor cover him, nor per- 
mit his firing from them. To prevent this, obstacles may be 
placed in front, or a ditch may be dug outside which will place him 
so far below the top of the wall or the bottom of the loop-holes 
that he cannot fire over the one or through the other. A total 
height of 6 ft. will prevent this, or, in case of loop-holes close to 
the ground, the maximum height should not be greater than 1 ft. 
from the outside, or an embankment made in rear 18 in. high. 

Notwithstanding these precautions, walls may still give cover; 
hence they should be flanked when possible. 

162.— In preparing walls for defense, the following cases 
arise:— 

(1) A wall less than 4 ft. high. Sink a small trench on the in- 
side to gain additional cover. Fire over the top. (PL 24, Fig. 1.) 
Head cover should be provided with logs, sand-bags, or sods, sand- 
bags being the best, sods next. 

Additional protection against artillery may be obtained by heap- 
ing earth from the ditch in front against the wall, the thickness 
depending on the kind of artillery the wall is to resist. 

If this should be done, the ditch should not be too close to the 
wall. A trench should be dug in rear to give cover to the supports, 
or for the firing line when not firing from the wall. 

(2) A wall between 4 and 5 ft. can be used as it stands, subject 
to the same modifications as in the preceding case. (Fig. 2.) 

(3) Between 5 and 6 ft. a wall can be notched. The tops of 
the notches may be filled with sand-bags, sods, etc. (Fig. 3.) 

(4) Should the wall be higher than 6 ft., a platform or staging 
must be raised inside to enable the men to fire over the wall or 
through the notches, or else the wall must be loop-holed. 

163.— Loop-Holing 1 . Loop-holes for fire should not be closer 
than 2 ft. 6 in.; ordinarily they should be 3 ft. To find the height, 
hold the rifle in the position intended to be used. 

164.— To make a loop-hole in a wall (Fig. 4), 14 in. or less in 
thickness, begin on the inside, to prevent the splay being toward 



Defense of Localities. 89 

the outside, by detaching a stretcher: the adjacent header on the 
outside can then be knocked out and the loop-hole roughly shaped. 
Outside dimensions, 4 in. wide by 3 in. high. Interior dimensions 
will depend on the nature of the ground over which fire is to be 
delivered. For horizontal fire increase the breadth, for elevated 
or depressed fire increase the height. 

In walls of ordinary thickness, a loop-hole can be made in 
about 15 minutes, a notch in about 5 minutes. 

165.— For a thick wall (Fig. 4), the small part should be at the 
center, the loop-hole splayed to the front and rear, for it will do 
this anyway. The side toward the enemy may be stepped, in 
order that bullets striking it may flatten. Loop-holes of observa- 
tion should splay towards the outside. 

All loop-holes, when not in use, should be blinded. 

166.— The height or position of the loop-hole is influenced as 
follows:— 

(1) 1 ft. above the ground. Men lying down in a shallow exca- 
vation. Earth heaped up to 18 in. in rear prevents the enemy 
from using the loop-holes should he close on the wall. The loop- 
holes are a difficult mark for the enemy and sentries at night can 
watch the sky line. Cannot be used where ground in front is 
broken. 

(2) Loop-holes 2 ft. 3 in. Sitting. Position easy, but must have 
a deep ditch in front. 

(3) Loop-holes 3 ft. Kneeling. Position strained and must 
have a deep ditch in front. 

(4) Loop-holes 4 ft. 4 in. Standing. Good command, but easier 
mark for enemy: ditch necessary, but not so deep as in cases 2 
or 3. 

(5) Loop-holes 6 ft. or more. Men standing on banquette. Best 
position for view or fire; no ditch in front; banquette strengthens 
wall, but takes longer to prepare wall in this manner; more sus- 
ceptible to artillery fire. 

167.— In order to allow a double tier of fire, walls should be at 
least 9 ft. high. (Figs. 5 and 6.) 

168.— Fences. Fences should be removed or left standing 
according to their position or direction. Wire fence forms a good 
obstacle; a rail or plank fence forms a screen and may be banked 



PLATE. 25, 



Figure 1 



Figure 2 



Figure 6 





| ^Figure 7- 




TH.% ■ 



Defense of Localities. ( Jl 

with eartli to give cover. If fence is of stone it may be treated as 
explained for walls. 

169.— Hedges. Almost the same principles as explained for 
walls apply to hedges. A hedge primarily acts as a screen, but to 
resist projectiles must be banked up with earth. 

Hedges possess the following advantages: (1) With little labor 
afford good cover. (2) Serve as a screen and also as a revetment. 
(3) Act as an obstacle to the enemy. 

To derive these advantages hedges can be treated as follows:— 

(1) A hedge w r ith a ditch on the defenders' side. Can be used 
as it stands, the ditch being converted into a trench, widened and 
improved if necessary. (Fig. 7.) 

(2) A hedge with a ditch on the enemy's side. Deepen the 
ditch if necessary, and throw the earth to the defenders' side to 
give cover. If this is not possible, scatter the earth and dig a 
trench in rear. (Figs. 8 and 9.) 

(3) A hedge with ditches on both sides. Deepen the ditch on 
the enemy's side, using the earth to obtain cover. Trench on de- 
fenders' side may be deepened. (Fig. 9.) 

(4) Hedge on sloping ground. Gain cover by a small trench in 
rear; scarp away the ground in front, forming a glacis. (Fig. 10.) 

(5) High and strong hedges. When time is available, may be 
treated as in Fig. 11. This is advantageous where additional com- 
mand is required. 

(6) A sunken road with hedges on both sides. Dig a shelter 
trench in rear of the hedge on defenders' side and utilize the earth 
to form a breastwork. Cut down the hedge on the enemy's side, 
entangling it to form an obstacle. 

(7) Hedge without ditches. Excavate a shelter trench on de- 
fenders' side and bank up the earth against the hedge as a breast- 
work. 

Weak places in hedges should be closed up with boughs, stakes, 
wire, etc., as a strong hedge, in addition to being a screen, forms a 
very efficient obstacle. 

170.— Embankments may be defended:— 

(1) Narrow Embankments. By occupying the inner edge bet- 
ter cover is obtained, but, unless the bank is both low and narrow, 
there is a dead space in front at the foot of the outer slope. (PI. 
25, Fig. 1.) 



92 Defense of Localities. 

(2) Broad Embankments. By occupying the front edge, a bet- 
ter field of fire is obtained, but less cover can be provided for 
the firing line, and the supports are exposed when coming into 
action. (Fig. 2.) 

171.— Cuttings are usually defended on the defenders' side, 
since in this case retreat is easy and the cutting itself forms an 
obstacle to the enemy's advance. But for active defense the front 
edge may be held, and then a forward movement is possible. In 
this case a means of retreat must be provided. 

172.— Fig. 3 shows a case where the fall of the ground admits 
of both sides of the cutting being occupied, giving a double tier of 
fire. The command of the higher edge over the lower should be 
about 6 ft. 

173.— In case of a road cut, as in Fig. 4, the upper fence may 
be used to sustain a breastwork, while the hedge below may be 
converted into an obstacle. 

174.— Woods.— (PL 26, Fig. 6.) Preparation of edge of wood 
occupied. The edge of a wood should be put in a state of de- 
fense and an abatis is the readiest means of doing it. The sali- 
ents should first be prepared, the reentrants next, and then roads 
entering the wood from the enemy's side. Instead of an abatis, 
the outer trees may be left standing and an entanglement made 
by packing in among them smaller trees cut about 10 to 20 paces 
to the rear. This clearing will serve as a communication all round 
the edge of the wood. 

If a reentrant bend is deep the abatis or entanglement may be 
carried straight across it and flanked from the adjacent salients. 
In case of a road, a lunette may be used instead of the abatis or 
entanglement. In case there is not time to prepare the entire 
edge of the wood, the salients may alone be prepared, the flanks 
of the defense being turned back for a short distance into the 
wood. 

175.— Preparation of woods lying beyond. Woods beyond, 
within rifle range of the line of defense, but too far to the front to 
be occupied, and too extended to be felled, should have an abatis 
or entanglement on the rear side to act as an obstacle. 

176.— Cover. Trench digging is difficult on account of the 
roots, but when possible it should be done. Cover is generally 
obtained from the natural features. Trees, unless very large and 



PLATE 26. 




94 Defense of Localities. 

standing thickly, do not give complete protection against artillery 
lire. Troops as supports and reserves, if not so far to the rear as 
to preclude their seeing through the wood to the front, may be 
covered by log walls and trenches. 

177. — communications, (a) There must be good radial com- 
munication as well as free movement along the boundary in rear 
of the firing line. 

(b) Roads and paths for bringing up the supports must be clear- 
ly marked by blazing as well as by posting sentries at all cross 
roads. 

(c) In dense woods, preparations should be made for blocking 
up roads by cutting trees on either side of them nearly through, 
to be pulled down across them in case of retreat. 

178.— Second and third lines may be placed along any open 
space, brook, or broad road, parallel to the front. In case of brook, 
the brook should be in front of defenders' position. 

179.— Artillery should generally be placed outside of the 
wood on the flanks. If placed in the wood, batteries should be 
placed far apart, near good roads, masked as much as possible, 
and each gun having more than one position. Reentrants are 
desirable. 

The number of defenders is estimated at 2 to 3 men per yard of 
front. 

180.— Stockades. Stockades are timber defenses, made by 
placing one or more rows of timbers or rails upright or horizon- 
tally, and so close to one another as to keep out rifle bullets, loop- 
holes being made, through which fire is delivered. They have the 
advantages of combining a parapet and an obstacle in one, giving 
good cover and ample interior space, and of being easily guarded 
against surprise. On the other hand, they require considerable 
time for construction, a certain amount of skilled labor, and are 
easily destroyed by artillery fire. 

181.— Stockades would be employed: — 

(1) Where timber is plentiful. 

(2) When artillery fire is not to be resisted. 

(8) When acting purely on the defensive. They are useful for 
the rear faces or gorges of half-closed works, and may he a good 
deal used in the defense of houses, streets, villages, and even woods. 



Defense of Localities. 95 

182.— Stockades of vertical timbers. Vertical timbers should 
be close together, planted in the ground to a depth of 3 or 4 ft., 
according to their size and weight, pointed or spiked at the top, 
and loop-holed at intervals. A ribband must be spiked along the 
inside, near the top, to keep the timbers close together. 

183.— PI. 25, Figs. 5, 6, and 7, show stockades with squared tim- 
bers; Fig. 8 with round timbers squared where they touch and the 
joint between every two trees made good on the inside by a 
smaller tree. 

184.— The loop-holes should be made in the crack between the 
timbers, in order to avoid weakening them, half being cut out of 
each. (Fig. 9.) In round timber, two saw cuts will make a loop- 
hole. (Fig. 10.) 

185.— The loop-holes should be cut before the timbers are placed 
in position and the same precautions in regard to them as given 
in walls should be observed. A loop-hole can be cut in from 10 to 
15 minutes. 

186.— In the foregoing cases, where the stockade is built of tim- 
bers placed vertically, squared timbers are preferred, as they are 
more easily fastened together and the joints made bullet-proof. 
In round timbers the logs should be as straight as possible. If 
very crooked, two complete rows will be required. 

One N. C. O. and 10 men will erect 15 running feet of stockade 
of squared timber, with one tier of loop-holes, in 8 hours. 

187.— Stockades of horizontal timbers, iron rails, fascines, or 
logs. (PL 26.) 

Fig. 1 shows stockade of rails and ties. Can only be used for a 
very short distance, as it will involve an immense amount of plant. 
Can be used to cover guns, close a road, and is more properly a 
barricade. 

Fig. 2 shows a stockade or log breastwork, banked in rear with 
earth held in place by planks or hurdles and stakes. 

Fig. 3 shows a stockade or breastwork of logs and fascines. 

188.— Stockade work, both vertical and horizontal, can be used 
for the construction of tambours (Figs. 4 and 5) and caponiers for 
flanking walls or stockades and covering entrances. Tambours 
may be triangular or rectangular in shape, arranged for one or two 
tiers of fire, and covered with a splinter-proof roof. 
-7- 



96 Defense of Localities. 

189.— Buildings. Buildings may be used for defense, either 
singly or in combination: — 

(a) As tactical points in the battle-field, held either as advanced 
posts, or as supporting points in the line or on the flanks, or as 
rallying points to cover retreat. 

(b) As keeps to a more extensive position, such as a wood, vil- 
lage, etc. 

(c) As an isolated post on the lines of communication. 

190.— In order to admit of use as a defensible post, a building 
should possess the following requisites:— 

(1) Solidly built of soft stone, brick, or adobe. 

(2) Large enough to hold at least half a company. 

(3) Sheltered from distant artillery fire; otherwise the building 
cannot be held against infantry or cavalry. 

(4) Well selected for the object in view. 

(5) Low, flat roof. 

(6) Clear field of fire obtainable. 

(7) Shape in plan affording flank defense. 

191.— The building should be looked upon as a keep, or second 
line of defense, a first line being prepared at a minimum distance 
of 40 yds. to the front, this distance being the least that will 
give the defenders immunity from splinters caused by shells strik- 
ing the building. 

192.— In falling back, the first line should retreat past, not 
into the house, which should by this time be occupied By the sup- 
ports. The garrison of the house may be estimated at two men to 
each door, window, or loop-hole, with a reserve of one-fourth, tac- 
tical unity being in this, as in all similar cases, adhered to as much 
as possible. 

193.— The following are the steps which must be taken in has- 
tily preparing a house for defense:— 

(a) Remove the inhabitants, also all easily combustible mate- 
rial, and provide water and heaps of earth in each room. 

(b) Barricade doors and ground-floor windows (bullet-proof if 
possible), also mask inaccessible windows, and remove all glass. 

(c) Make loop-holes in doors, shutters and walls, and, in the 
case of a sloping roof, remove tiles or slates. 



Defense of Localities. 97 

(d) Clear away cover in the vicinity as far as time and means 
will allow. 

(v) Open up communication throughout and prepare a means of 
retreat. 

194.— The same precautions as to loop-holing walls apply in case 
of buildings. On the ground lioor the horizontal dimensions of a 
loop-hole should be' greatest; on upper floors, the vertical dimen- 
sion. If an artillery attack is feared, shelter trenches should be 
provided outside the building on the flanks. 

195.— Barricades for Doors may be made in the following 
ways:— 

(a) Fill boxes, barrels, cupboards, etc., with earth and place 
them against the door imide. 

(b) Build a wall of brick, stone, flag-stones, or hearth-stones, 
against the door inside, and support by a shutter or another door. 

(c) If railway plant is available, pile ties horizontally on one 
another and secure with telegraph wire. 

(d) Pile lumber inside the door and fix with blocks nailed to 
the floor. 

(e) Other methods may be employed in accordance with mate- 
rial available. 

196.— Should a door be reserved for use, it should be in a re- 
entering angle of the building, if possible, and protected from fire. 
A couple of chests filled with earth and placed on rollers may be 
used to secure the door. Similarly it may be possible to place iron 
or wood on the door, thus rendering it bullet-proof. 

197.— Windows. Windows must be barricaded as explained 
for doors. If provided with shutters, these should be utilized. 
Upper windows require to be bullet-proof only high enough to 
cover the defenders. Bedding is no protection against modern 
rifles, but may be used to mask windows of upper floors. If tim- 
ber is used it should be placed vertically and nailed to horizontal 
ribbands strutted back to the floor. 

198.— If the house is large and strong and is to be held to the 
last, in addition to the foregoing the following preparations should 
be made:— 

(1) Arrange for storage of provisions and ammunition. 

(2) Set apart a place for a hospital. 



PLATE 27, 



Fig.l 



Fig 2. 




Kg.©, 







Defense of Localities. 99 

(3) Prepare latrines. 

(4) Loop-hole partition walls and upper floors. 

(5) Make ready barricades to cover retreat from one part of the 
building to another. 

(6) If artillery is feared, shore up the floors and cover them 
with about 3 in. of earth. 

199.— Should the construction of the house not afford suffi- 
cient flank defense, it can be improvised in the shape of tambours 
or caponiers, but the labor involved in their construction is consid- 
erable and they would only be undertaken for the defense of a 
very long wall or to cover an important entrance or communi- 
cation. 

For the latter purpose a machicoulis gallery is sometimes em- 
ployed. (PL 27, Fig. 3.) This is made by removing the wall of 
the upper story where a window occurs down to the level of the 
floor, running out two or three long balks so as to project a few 
feet beyond the wall, the other ends being secured down to the 
floor. On these planks are nailed, with holes cut through to act 
as loop-holes, and a musket-proof parapet of planking, sand-bags, 
etc., is built all around. A projecting veranda offers a favorable 
position for this arrangement. 

Second method: If a regular gallery can not be made, holes 
may be cut in the wall at a convenient height for a man to fire 
downwards when leaning over, and a screen of wood or other 
material may be secured outside for protection. (Fig. 4.) 

If neither of the foregoing methods be possible, holes may be 
made in the roof, through which grenades may be thrown on the 
enemy. 

200.— The materials most likely to be useful in preparing a 
house for defense are sand-bags, stout timbers, such as railway 
ties, large boxes, chests, barrels, coal-boxes, furniture and bed- 
ding. 

201.— PL 27, Figs. 1, 2, and 5, illustrate the more important 
points in the defense of a house. 

202.— Farms. Farms should be defended according to the 
nature of the surface covering, the ground and the improvements, 
and may involve the preparation for defense of walls, hedges, cut- 
tings, embankments, buildings, woods, etc. Owing to their posi- 
tions, farms may become very important and a great amount of 



100 Defense of Localities. 

fighting take place for their possession. They may occur either 
in the main line of a position, as an advanced post in front, or as a 
reserve station or rallying point in rear. 

203.— Fig. 6 shows the principles of defense applied to a farm 
lying in advance of a stream, which is a point that requires to be 
strongly held. From the position of the farm it must be held as 
an advanced post. 

The firing line is established along the fences bounding the 
fields and orchard. The farm buildings are loop-holed and can 
be held should the firing line be forced, while the fire from the 
house would render occupation of the farmyard by the enemy 
difficult. Further to the rear, the wood is strongly prepared for a 
final position, as shown in the figure. 

204. — The rear of an advanced post should be left weak and 
open to facilitate recapture. 

205.— Villages. Villages can be rapidly prepared for defense 
and, under favorable circumstances, obstinately defended; conse- 
quently they are valuable supporting points in a defensive line 
Owing to the effect of modern artillery and the liability of burst- 
ing shells to set villages on fire, great precautions have to be taken 
in the preparation for defense. 

206.— A village, when properly prepared and defended, may 
have the following advantages:— 

(a) Can be rapidly placed in condition for defense. 

(b) Defense may be obstinate— thus giving time. 

(c) Conceals the strength of the defenders. 

(d) Provides a certain amount of cover from fire. 

(e) Shelter from the elements. 
On the other hand:— 

(a) The garrison is scattered, and hence the difficulty of 
supervision. 

(b) When under artillery fire, splinters may cause many 
casualties. 

(c) Liability to be set on fire by shells. 

207.— A village may be held with the following objects in 
view:— 

ftfJ~As a supporting point in the main line of defense, 
(b) As an advanced post in front of the main line. 



PLATE 28. 




M House demolished 
E3 House left standing 

\ — | , prepared for 

demoliUoJi. 
§§3 - prepared for defense. 
— — Entrenchment. 
ESSE #fr* entanglement ^£<3SSS£^ 




102 Defense of Localities. 

(c) As an independent post. 

(d) As a reserve station or rallying point in rear. 

In the first case, strengthen the front and flanks. The rear 
should be prepared to resist infantry. In the second case, the 
distance from the main line will govern the amount of prepara- 
tion. If very distant, should be prepared for all-round defense. 
If within rifle range, the rear should be left open, so that in case 
the village is taken, recapture will be facilitated. In the third 
case, if an independent post, must be prepared for an all-round 
defense. In the fourth case, if in the rear of the main line, must be 
prepared for a protracted, all-round defense. 

208.— Whether or not a village is to be held will depend on:— 

(1) Its tactical value as compared with the number of men re- 
quired to defend it. 

(2) Whether it is practicable to provide a sufficient garrison for 
its defense. 

(3) Whether it will be possible to demolish the village entirely, 
in order to deprive the enemy of the cover it provides. 

(4) On the form and nature of the surrounding country— L e., 
no commanding ground within artillery range, foreground easily 
prepared and the unimpeded advance of the defenders' troops in 
the required direction easily arranged. 

(5) On the shape of the village— whether broadside, salient, or 
circular. 

(6) Nature and materials of the houses. 

209.— The first points to determine in preparing a village for 
defense are how much of it will be defended, whether there are 
buildings suitable for a keep or citadel, and whether or not these 
are properly located. 

210.— The arrangements for defense would be made in the fol- 
lowing order:— 

(1) Clear the ground toward the enemy. (See Chap. V.) 

(2) Cover for the firing line, supports, and reserves. (See 
Chap. IV.) 

(3) Creating obstacles. (See Chap. VI.) 

(4) Preparing communications. (See Chap. XVII.) 

(5) Constructing retrenchments, citadels, or keeps. (See "Build- 
ings.") 



Defense of Localities. 103 

211.— The garrison of a village may be estimated at two men 
to the yard of perimeter to be defended. 

212.— Salient Village. (PL 28, Fig. 2.) The successive lines 
of defense must be carried well out to both sides and the flanks 
well protected; otherwise the enemy may turn them and avoid 
fighting in the streets. 

213.— Broadside Village. (Fig. 1.) Here the outside fences 
must be more utilized than the actual buildings, as the latter are 
open to fire from artillery. 

214.— Circular Village. (PL 29.) Great attention must be paid 
to the proper division of the village into ^sections for defense and 
preparing and making the communications. 

215.— In any of the foregoing cases, if cover does not exist foi 
supports and reserves, it must be provided, as the village will prob- 
ably be shelled before being assaulted. 

If artillery is to be used it should be placed on commanding 
ground, inaccessible, if possible, to the enemey, and so that its^ 
fire will sweep those parts most favorable to the enemy's advance. 



PLATE 29. 




CHAPTER XIV.— Use of Cordage and Spars. 



216.— A rope is composed of three or more strands of fibrous 
material, iron or steel, twisted together. The strands of fibrous 
ropes are formed of threads; of iron and steel ropes, of wires. The 
size of rope is denoted by its diameter in inches,* and rope is gen- 
erally sold by the pound. Fibrous ropes when new and dry stretch 
considerably, when wet they contract; advantage is often taken of 
the latter fact to tighten temporary lashings. Manila rope is only 
about % as strong as hemp rope; tarred ropes only about % as 
strong as untarred. 

217.— A rule approximating to the breaking weight of a new rope, 
in tons of 2,000 lbs., is to take one-fourth the square of the circum- 
ference in inches. The strength of pieces from the same coil may 
vary 25 per cent. 

Ropes in daily vse should not be worked up to greater than 1-5 
their breaking loads, to meet the reduction in strength by wear 
and exposure. 

218.— The following table gives the approximate breaking 
loads and weights of new Manila ropes, Swede's hemp center 
Iron pliable ropes of 6 strands of 19 wires each' and hemp center 
Steel pliable ropes of 6 strands of 19 wires each, Manufacturers' 
Tests: 



Diaru. in 
inches 



Breaking loads in lbs. 



Manila 



Steel 



Weight per 100 
ft. in lbs. 



Manila 



|Iron& 
Steel 



Minimum Size of 

Sheaves in feet 
for Iron and Steel 



1-4 


780 | 


I 


| 


3 | 






3-8 


1,280 | 


5,000 | 


| 


5 


26 


1 


7-16 


1,562 | 


6,200 | 


12,000 | 


61-8 


29 


1% 


1-2 


2,250 | 


7,600 | 


15,000 | 


8 


35 


2 


5-8 


4.000 | 


11,000 | 


24,000 | 


13.5 


| 70 


2% 


3-4 


5,000 | 


17,500 | 


36,000 | 


16.5 


| 88 


3V4 


7-8 


7,500 | 


23,000 | 


50,000 | 


24 


| 120 


3% 


1 


9,000 | 


32,000 | 


66,000 | 


30 


| 158 


4 


1% 


14,000 | 


54,000 | 


104.000 | 


45 


250 


5 


iy 2 


20,250 | 


78,000 | 


154,000 | 


66 


| 365 


6y 2 


i% 


30.250 | 


108,000 | 


212,000 | 


97 


| 525 


7y 2 


2 


36,000 j 


130,000 | 


250,000 | 


115 


630 


9 



*In the Navy the size of rone is denoted by its circumference in inches, 
method used should be distinctly stated. 



The 



106 Use of Cordage and Spars. 

219.— Knots, Hitches, etc. The standing part of a rope is any 
part not an end. 

A bight is a loop formed in a rope. (PI. 30, Fig. 1.) 

Whipping is securing the end of a rope with twine to prevent 
it from fraying out. (Fig. 1.) 

Parceling is wrapping a rope to prevent chafing or cutting 
against a rough surface or sharp edge. (Fig. 1.) 

Stopping is fastening two parts of a rope together without a 
crossing or riding. (Fig. 1.) 

Seiz'mg is fastening two parts of a rope together with or with- 
out riding and finishing with crossings or f rapping turns. (Figs. 
5 and 17, trapping turns not shown.) 

Nippering is taking turns crosswise between the parts to jam 
them, finishing with crossings or trapping turns, latter not shown 
in figure. (Fig. 1.) 

Splicing is joining the ends of ropes by opening the strands 
and placing them into one another (Figs. 2 and 3), or by putting 
the strands of the ends of a rope between those of the standing 
piart. (Fig. 4.) The splice is about % wieaker than main rope. 

Rolling or stopper hitch, for fastening a rope to a strap or tail 
block, and to secure a fall while being shifted on a windlass or 
capstan. (Fig. 5.) 

Overhand knot, to prevent the end of a rope from fraying out, 
from slipping through a block, and the beginning of several other 
knots. (Fig. 6.) 

Figure of 8 knot, for same purpose as overhand knot and used 
in making cask piers. (Fig. 7.) 

Square or reef knot, for joining the ends of two ropes the same 
size. (Fig. 8.) 

Thief Imot (Fig. 9), with ends on opposite sides, and Granny knot 
(Fig. 10), by crossing the ends the wrong way, both looking like 
square knots, are to be avoided, as they will not hold. 

Single bow or slip knot. (Fig. 11.) 

Square borv, which can be cast off. (Fig. 13.) 

Marlinspike hitch, used in putting on lashings, etc. (Fig. 12.) 

Shcepsnank, used to shorten a rope temporarily without cutting. 
(Fig. 14.) 

Two half hitches, for fastening the end of a rope around its own 
standing part. (Fig. 15.) 



PLATE 30. 




FTG.l. 



x ms a m 



anehn8 yss^- N( pp eH % 



? 







Rolling or Stopper Hitch, seizing 

PT , jfr&u* m.7. mro - ™- 9 - n&m 

FIG. 6. . ^^ FIG.8. 




Overhand Jmot M 8 ure ¥ 8 

FIG. 11.^ FIG. 12. 





Sitwle bow* slip knot , r 7f .* Square or J Thief Grwuw 

FIG. 13 MarkfyiZe. ^¥FIG.14 

nitcrv. 




PLATE 31. 



FIG: I 



FIG.Z 



FIG.2L FIG.4. v FIG.5. 



J3owline 
oiv a bioht 



FIG.12. 





fend 



FIG.13. 



'Hack lashing 

FIG15. 




Tiack lashing 

FIG.14. 





/Square JLashing 

FIG.16. 




Shear Lashing 



Gin lashing EAff. 



Use of Cordage and Spars. 109 

Round turn and two hiilf hitches, to secure guys to stakes, etc. 
(Fig. 16.) 

Fisherman's bend or Anchor knot, for fastening a rope to an 
anchor or ring. (Fig. 17.) 

Weaver's knot or sheet bend, for joining ropes of different sizes 
without jamming. (Fig. 18.) 

Double sheet bend, more secure than the single bend. (Fig. 19.) 
Clove hitch, for fastening a rope to a spar; the end may after- 
wards be stoppered to its own part. The clove hitch differs from 
two half hitches only in being made around a spar or other rope 
instead of around its own standing part. (Fig. 20.) 

Timber hitch jams when made round a timber. (Fig. 21.) 
Bowline, to form a temporary loop at the end of a rope. (Fig. 
22.) 

Bowline on a bight, to make a loop on a bight. (PI. 31, Fig 1.) 
Cat's paw, for applying a purchase or tackle to the fall of an- 
other. (Fig. 2, the beginning; Fig. 3, how applied.) 

Blackwall hitch, for fastening the end of a rope on a block in the 
simplest manner, or fastening a rope in a hook. (Fig. 4.) 

Mousing is a seizing placed around a hook to prevent it from 
spreading or unhooking. (Fig. 4.) 

Car rick bend, to fasten guys to a derrick. (Fig. 5.) 
Lark's head, for fastening a bight to a ring. (Fig. 6.) 
Capstan or Prolonge, making fast a spar. (Fig. 7.) 
Wall knot, for finishing off the end of a rope to keep from un- 
stranding (Fig. 8), by passing the strands, as shown, then drawing 
them down into a knot. 

Frapping is passing a rope around a lashing to keep the turns 
together. (Figs. 14, 15 and 1G.) 

Straps are rings used for attaching tackles to spars or ropes. 
(PL 33, Figs. 1, 2 and G.) 

220.— To make a short splice. (PI. 30, Fig. 2.) Unlay strands 
of each end for a convenient length; take an end in each hand, 
place end to end, strands sandwiching, and grasp the three strands 
from opposite rope in left hand. Take a free strand, pass it over 
the first strand next to it, then through under the second and out 
between the second and third from it, then haul taut. Pass 
each of the remaining six strands in same manner, first those of 



110 Use of Cordage and Spars. 

one end and then those of the other, and so continue as far as 
desired. 

221.— To make a long splice. (Fig. 3.) Unlay strands of each 
end, three or four times longer than for short splice, and place end 
to end as described. Unlay one strand a considerable distance and 
till up its space with opposite strand from other rope, and twist 
them together. Do the same with two strands on other rope. 
Open remaining strands, divide in two, make overhand knot with 
opposite halves, and lead ends as in short splice. Cut off the other 
two halves. Do the same with the other pairs of strands 
where twisted together. Before cutting off any of the half strands, 
first stretch, roll under the feet, and pound the rope well. This 
splicing does not increase the size of the rope and is used where 
the splice is to run through blocks. 

222. — To make an eye splice. (Fig. 4.) Unlay one end for 
short distance, lay strands upon the standing part so as to form 
the desired sized eye. Put first end through the strand next to 
it. Put second over that strand and through second. Put third 
through third strand on other side of rope and so continue. This 
forms a permanent loop in end of rope. 

223.— To sling a box or barrel. Lay a strong strap under 
it, spreading the parts, and pass one bight through the other; or 
make a long loop with a bowline and sling as shown on PL 31, 
Fig. 9. If one head is out stand barrel up, put one part of a strap 
under middle of bottom, take a half hitch over top with each part 
just over bilge hoops and exactly opposite; or place rope under 
barrel, bring up over top, make overhand knot, open it out and slip 
each half down over hoops, fasten end to standing part with bow- 
line. (Fig. 10.) 

224.— Back lashings (Figs. 11, 12 and 13) are made with a 1-3 
in. rope, 18 ft. long, with a loop at one end, and a rack stick 2 ft. 
long, 1% in. in diameter, having a cord 4 ft. long through one end, 
by passing the rope two or three times around the side rail and 
balk, and, after making it fast, twisting it tightly with the rack 
stick. 

225.— Transom lashing. (Fig. 14.) The spars are laid across 
each other at right angles, a clove hitch is made on one of the 
spars, the end then twisted around its standing part, then three 



PL&IE 32, 




FIG.3. •_ 




FIG. 5. 



icket <EkBecket 

«% ^ 3& 

fMG.6 



FIG. 7. 



FIG.10 




Xf-^-tu 7 firry Block 
unarm Moat ' 




112 Use of Cordage and Spars. 

or more turns are taken around the spars, under one and over the 
other, keeping outside previous turns on one spar and inside on the 
other. Several trapping turns are then taken between the 
spars and the end fastened on one of the spars with a. clove 
hitch. Used in lashing transoms to standards in bridge-building. 
226.— Shear lashing. (Fig. 15.) The spars are laid parallel, a 
couple of inches apart, on a block, a clove hitch made on one spar, 
then five or six turns taken around both spars without riding. 
Several frapping turns are then taken between the spars and the 
end fastened on one of the spars with a clove hitch. This is used 
in rigging shears for hoisting heavy weights, etc. 

227.— Gin lashing. (Fig. 16.) The three spars are laid par- 
allel, a couple of inches apart, the butts of the two outside ones 
in one direction, that of the middle one in the opposite direction. 
A clove hitch is made on one spar, then five or six loose turns 
taken, passing over and under, without riding. Several frapping 
turns are taken in each interval and the end fastened on one of 
the spars with a clove hitch. 

228.— Blocks, Tackles, etc. A pulley consists of a wheel, hav- 
ing a grooved rim for carrying a rope, turning in a frame. (PL 
32, Fig. 1.) 

A block (Figs. 2 and 3) consists of one or more grooved pulleys 
or sheaves turning on an axle, called a pin, mounted in a casing 
or shell, which is furnished with a hook, eye or strap on one end, 
by which the block may be attached to something, and sometimes 
with a becket on the other end for attaching ropes, etc. It is 
used to transmit power, or change direction of motion, by means 
of a rope or chain passing round the movable pulleys. Blocks are 
single, double, treble or fourfold, according as the number of 
sheaves or pulleys is one, two, three or four. The size of blocks 
is expressed by the length of the shell in inches. A common style 
of Ferry Block is shown in Fig. 5. 

A snatch block (Fig. 4) is a single block with a notch cut in one 
cheek so as to receive the standing part of a fall without the trou- 
ble of reeving and unreeving the whole. 

A running block is one attached directly or indirectly to the ob- 
ject to be raised or moved; a standing block is one fixed to some 
permanent support. 



Use of Cordage and Spars. 1 1 3 

229.— A tackle consists of two or more blocks with a rope rove 
through them for use in hoisting. 

230.— The parts of all ropes between the points of fastening 
and sheaves are called standing parts; the parts between the 
sheaves are called running parts; the part to w r hich the power is 
applied is called the fall. 

231.— To overhaul a tackle is to separate the blocks; to round in 
is to bring the blocks closer together. 

A tackle is said to be block and block or two blocks when the en- 
tire fall is hauled through so the blocks are in contact. 

232.— Before reeving a rope in a block, it should be stretched 
out its full length. Tackle should not be allowed to twist; to pre- 
vent it, iusert a bar in the block or between the running parts and 
use it as a lever to hold straight. If allowed to make one complete 
turn with two single blocks, the friction will increase the resist- 
ance about 40 per cent. Ropes should not be too large for blocks, 
the rule being, "Small ropes and big blocks" 

233.— Power of Tackle. Theoretically, the power necessary 
to just balance a weight, with a tackle of two blocks, is equal 
to the weight divided by the number of ropes at the running 
block, including the standing part if attached to it. 

234.— To produce motion, how r ever, a greater power is required 
to overcome friction and stiffness of rope. It has been found by ex- 
periment that to do this about 10 per cent of the theoretical power 
necessary to balance must be added to itself for each of the 
sheaves over which the rope passes, the blocks being in good con- 
dition and w^ell oiled. If not in good condition and not well oiled, 
the per cent may be as high as 30 for each sheave. 

235.— The formula P = w * 1,s is used to determine the power 
required to raise a weight with a simple tackle, in which P = the 
power required, W = the weight to be raised, S = the number 
of sheaves, and R = the number of ropes at running block, in- 
cluding standing part if attached to it. If it is required to find 
how great a weight a certain pow r er will lift, the formula is 

W = ^ys^' Power is gained only at the loss of time. The power 
moves as many times faster and farther than the weight as the 
number of ropes at the running block. No advantage is gained 



PLATE 33. 




field Capstan 




m^mm ^ 



&:*m 



^3* 



art 



Seclioi 




Use of Cordage and Spars. 115 

by using, in one fall, a greater number of sheaves than two 
treble blocks, but further advantage may be gained by a combina- 
tion of blocks and tackles.* 

236.— A squad of men hauling on a fall exert a pull of about 
80 lbs. (or half their weight) each, the fall being nearly horizontal. 

237.— A Derrick (Fig. 7) usually consists of a single spar or 
leg, held up by four guys, and having a tackle lashed to the top, 
used for hoisting or lowering heavy bodies within a circle whose 
diameter equals % the height of the spar. When made of two 
legs (Fig. 8), they are mortised into a cap on top and a sill at the 
bottom, only two guys being required, a fore and back, but three 
are better, one fore and two back. The weight can only swing 
between the legs. The holdfasts for the guys should be at a dis- 
tance from foot of derrick at least twice its height. The foot 
should be secured from slipping by being let into a hole in the 
ground or otherwise. 

238.— Shears (PI. 33, Fig. 1) consist of two spars, of a size suita- 
ble for the weight to be raised, lashed together at the cross. 

A tackle is fastened at the lashing by a strap passed around it 
or otherwise, the hook moused, and holdfasts are required as for 
two-legged derrick. 

Two-legged derricks and shears should not lean to exceed 1-3 
of their height, and each leg should have about % this inclination, 
or 1-6 their height. 

239.— A Gin (Fig. 2) is a tripod formed of three poles. The two 
outside ones are called legs, the third one the prri-pole. Gins re- 
quire no guys. Weights can only be lifted vertically. 

240. — In using derricks, shears, and gins, the fall is generally 
led through a snatch-block lashed on a leg near the bottom, 
thence to a crab, windlass, or capstan. Derricks frequently 
have fastened on their legs a winch for transmitting the power. 
(PI. 32. Fig. 10.) 

241.— A Windlass (Fig. 12) consists of a horizontal axis fast- 
ened in a frame and turned by means of cranks or handles. The 
rope may either be fastened to the axis or passed two or three 
times around it. hauled taut, the free end being held, and taken 
in by men in the rear. 



*The formula P — -* — is merely a simplified form of the equation 
P^IW+^WSl -f- R. (See par. 234.) 



116 



Use of Cordage and Spars. 



242.— A Capstan (PL 32, Fig. 9, and PL 33, Fig. 3) consists of 
an upright barrel, either smooth or ribbed, arranged about a spin- 
dle. Above the barrel is the head with holes to receive the ends of 
levers or bars by which the barrel is revolved. The rope is passed 
and held as explained for a windlass. 

243.— Holdfasts are stout wooden stakes driven into the 
ground, or other arrangements used for securing purposes. 

An essential point to be considered before moving or suspend- 
ing heavy weights is the nature and condition of the securing 
points, together with the strain that will be brought upon them. 
In the first instance, it is better to make them more secure than 
seems to be absolutely necessary, as, when they once begin to 
give way, it is difficult to strengthen them. PL 33, Figs. 4, 5, 6 
and 7, show some of the various methods of making them, 
also PL 40a. 

243a.— An improvised Field Capstan, which is but an adapta- 
tion of the Spanish windlass, is shown in cut. One end of the rope 
is made fast to the object which is to be moved and the other end 
to a holdfast. A lever, a, is inserted in a bight of the rope and one 
end of it placed against an upright bar, I). The lever is then car- 
ried round and round the bar, which revolves and gradually winds 
the rope upon itself as it approaches the holdfast. The bar 6 can 
be held upright more readily if the lever a is long enough for men 
to work at both ends of it. 









* -^^^==^!S^ag^5lL' 



PLATE 34. 




CHAPTER XV.-Spar Bridges. 

244.— Military Bridges are not required to fulfill all the condi- 
tions of ordinary bridges. They are constructed for special and 
immediate purposes, usually with unskilled labor, and of such 
materials as can be procured on or near the spot. That the bridge 
built shall be strong enough to bear the heaviest load intended to 
be crossed is the first requisite; celerity and simplicity of con- 
struction next. 

245.— PL 34 is an illustration of what was done in building 
Military Railroad Bridges under unfavorable circumstances in 
time of war with troops of the line, very few of whom were 
mechanics, many could not even handle an ax, none were trained 
to the duty, and none were engineer troops. This bridge was built 
by General Haupt over Potomac Creek, Va., during the Rebellion, 
and was 80 ft. high and 400 ft. long. It consisted of three tiers 
of trestles on top of cribs 12 ft. high. The timber used was chiefly 
round sticks, cut in the woods near by, and put together without 
bolts, simply with spikes and wooden pins, and when finished, was 
crossed by 10 to 20 heavily loaded trains per day. This kind of 
work, however, properly belongs to a special construction corps, 
but it falls to the lot of the officers and men who first arrive at a 
stream on the ordinary roads, where there are no means of cross- 
ing, to construct an improvised bridge with such tools and of such 
materials as may be available. 

246.— The plans and expedients which follow have been select- 
ed with a view to their being types of bridges that can be con- 
structed by troops having no other tools than axes and augers, and 
such materials as growing trees found in the vicinity, and beams, 
boards, ropes, wire, nails, etc., obtained from neighboring houses 
and towns. The purposes for which the bridge is to be used, the 
nature of the crossing, velocity of stream, and kind of bottom, will 
determine its strength, kind, size. etc. 

247.— For a common road bridge, the load is assumed to be a 
maximum when covered with men, estimated at 120 lbs. to the 
square foot, plus the weight of the bridge, usually taken at about 
80 lbs. per lineal foot. For reasons which are evident, the bridge 
should be as short as possible, with good approaches. Swampy, 
high, or steep banks should be avoided. 

248.— Bridges usually take their names from some part of their 



Spar Bridges. 119 

construction, as Trestle, Truss, Pile, Suspension, or Floating Bridges. 
The distance between supports (determined by the strength of 
the balks to bear the desired load) is called the Day or span, and 
the corresponding part of the bridge the span. The superstruct- 
ure, consisting of the stringers or balks, the floor, the side-rails 
and the fastenings, is of the same nature for each kind, as shown 
in PL 35, Fig. 1. The ends of the balks rest on cross-pieces of the 
supports called transoms; on the balks (of which there are usually 
five) are laid chess or poles, forming the floor; on top of the 
floor, over the outside balks, are laid side-rails or poles, which 
are securely fastened every 4 or 5 ft. to the balks beneath by 
rack lashings. Hand-rails (Fig. 2) should always be provided on 
each side of the roadway. The usual width of military bridges is 
9 ft. in the clear, between side-rails; 6 ft. will answer for Infantry 
in column of twos, and Cavalry by file; 2.5 ft. for Infantry in 
single file. 

249.— For determining the strength of the materials to be used, 
all errors should be on the side of safety. The practical method 
is to place the ends of the timber on low supports, as far apart 
as they will be in bridge^ as many men as can then step on it 
and jump up and down; or it is otherwise arranged so as to 
bring as great a weight upon it as it will have to bear at any time 
in bridge. 

Where small poles of the usual number would not be strong 
enough, a greater number must be used until the desired strength 
is gained. 

250.— Transoms must be strong enough to bear all the weight 
that may be brought upon one bay of the bridge, considered as 
distributed dead load on the transom. 

251.— The load in pounds which any timber resting on two 
points of support will safely bear, concentrated at its center, may 

be approximately determined by the formula 1-3 x -y- x C, in 
which b = the breadth in inches, d = the depth in inches, 1 = the 
length in feet between supports, and C is a constant in pounds for 
the particular material of the beam,* 1-3 is the fraction of the 

*C is determined by taking a piece 1 in. square and 1 ft. longbetween supports, 
loading: it at the center until it breaks, then to the applied load adding one-half 
the weight of the piece between supports, and the sum will be C; or. a piece of 
any convenient size and length can be used, afterwards deducing what the 
breaking weierht would be for a piece 1 in. square audi ft. long, remembering 
that the Vreaking weight varies directly with the width, as the square of the 
depth, and inversely as the length. 



PLATE 35. 




Spar Bridges. 121 

breaking weight used for safety. It would, iu all cases, be better 
lo use a smaller fraction of the breaking weight, as 1-5 or 1-6; or 
even 1-8 in structures designed to be of a lasting character. The 
formula is for a rectangular beam, but for a cylindrical timber 
whose mean diameter equals the side of a square beam, use G-10 
of what the formula gives. 

252.— Weight brought on a bridge by the passage of troops, taken 
as distributed live load for Infantry and Cavalry: Infantry in 
column of twos or fours, about 225 lbs. per lineal foot. Infantry 
when crowded at a check in fours, about 550 lbs. per lineal foot. 
Cavalry in column of twos, about 230 lbs. per lineal foot. Cavalry 
when crowded at a check, about 350 lbs. per lineal foot. When 
Artillery carriages cross a bridge, the weight is not equally distrib- 
uted, but is greatest when the wheels bearing the heaviest load are on 
the center. 

253.— A uniformly distributed dead load produces only one- 
half the strain of an equal dead load concentrated at the cen- 
ter. A moving or live load produces twice the strain of a dead 
load. A uniformly distributed live load equals a concentrated 
dead load. 
Table of Constants C, for finding the breaking load of various 

materials by the formula ix b< j 2 * c when concentrated at cen- 
ter of beam supported at both ends. From Trautwine's 
"Engineer's Pocket Book": 

Ash, white 650 Elm 350 Oak, red & black..550 

Ash, swamp 400 Hemlock 400 Pine, white 450 

Ash, black 300 Hickory 700 Pine, yellow 500 

Beech, white 450 Hickory, pig nut. .500 Pine, pitch 550 

Beech, red 550 Locust 600 Poplar 550 

Birch, 450 Mahogany 450 Spruce 450 

Cedar 250 Maple 550 Sycamore 500 

Chestnut 450 Oak. white & live.600 Walnut 450 

254.— The cubic contents of a log is approximately equal to 
0.7854 times the square of the mean diameter times the length, 
or the area of the mean section multiplied by the length; or the 
square of one-fifth the mean circumference times twice the length, 
all in feet. 

255.— In calculating the strength of a round timber or spar, 



122 Spar Bridges. 

its mean diameter is used, because such a spar, if overloaded, will 
break at center, instead of at small end.* 

256.— The following table gives the weights in pounds per 
cubic foot of various materials: 

Iron, cast 450 Chestnut 40 Spruce 31 

Iron, wrought. . . .487 Cottonwood 35 Sycamore 37 

Lead 710 Hickory 43-49 Walnut 38 

Steel 488 Maple 48 Clay 120 

Ash 38-47 Oak 45-60 Earth 72-120 

Cedar 35 Pine 34-40 Gravel & sand. .90-130 

Green timbers weigh from 1-5 to 1-2 more than those in table. 

257.— When spars are used for balks, they must be arranged 
so as to have all butts or all tips together on a transom. They 
should have good overlap and be well lashed to each other and to 
the transoms. To allow for settling, the center is generally made 
higher by about 1-30 the span. 

258. — Stringer Bridge. For spa)n«s of 25 ft. or less, if timber is 
available, the simplest form of stringer bridge could be built, as in 
Fig. 2, of 6 balks, 30 ft. long, reaching clear across, covered with 
small poles 4 to 6 in. in diameter, 12 ft. long, for a floor. Side-rails 
would be laid on the floor over the outside balks and either lashed 
or pinned to the balks. Hand-rails would be as shown, or a rope 
stretched across would answer. Time of construction — 1 hour. The 
balks could be jumped across as shown in either Figs. 3 or 4. 

259. — Scarped Bridge. If stringers of length to reach across 



*For a bridee constructed ?>s in Fig 2, with six balks, to determine the safe 
load it will carry, the application will be about as follows: 

The balks being of 3 T ellow pine, 10 in in diameter at the center, 25 ft. be- 
tween supports, the formula gives T 6 f, x j X J£ 3 x 500 =4,000 lbs. as the safe load 
each balk will bear concentrated at the center> including its own weight. Cal- 
culating for five balks, on the supposition that the two outside ones receive only 
one-half the strain of the center ones, they will bear 5 x 4,000 lbs. = 20,000 lbs. 
concentrated at center. From this deduct half the weight of the balks and floor 
concentrated at center, found by multiplying one-half the cubic contents by the 
weight per foot; for the six balks this will be 

fi x H (P) 2 * -^854] x 25 x 40 = 1,636.25 lbs. 
For the floor of seventy-five 4-in. poles, each 12 ft. long, the weight will be 

75 x i x [ (JP x .7854] x 12 x 40= 1,570 86 lbs 

20,000 lbs. — 3 207.11 lbs = 16.792.89 lbs , the capacity of the bridge concentrated at 
the center. Infantry marching in column of fours crowded by a check would 
cause a load of only about 13,J50 lbs. Cavalry in column of twos crowded by a 
check only about 8.750 lbs. 

Similarly, knowing the span, the kind of material at hand, the weight to be 
borne, etc., the size of timbers required can be deduced; or, having the size and 
kind of the timbers, weight to be borne, etc., the greatest length that can be 
spanned can be determined by the above formula. 



PLATE 36. 




124 Spar Bridges. 

cannot be obtained or are too heavy to handle easily, a scarped 
bridge as in Fig. 5 might be made, requiring only axes and augers. 
The shore stringers, 25 ft. long, 10 in. in diameter, six on each 
shore, have their bridge ends scarped on upper side 18 in., then 
pushed out 10 ft., their shore ends being well anchored down and 
loaded with roadway. Six short stringers, 8 ft. long, 10 in. in diam- 
eter, three on each shore, scarped 18 in. on under side of each end, 
are passed over gap and laid on shore stringers. Two 2-in. auger 
holes are bored at each end through both stringers and wooden 
pins driven through, and the flooring completed. 

260.— Paine's Bridge. (Pig. 6.) If timber is abundant and 
stream not over 6 ft. deep, select trees up stream. Fell, and trim 
off branches. Bore two 3-in. auger holes near butt ends 3 in. apart, 
making an angle of 30° with each other, and a third hole, making 
an angle of 45°, between them nearer the butt. Cut and insert in 
outside holes legs long enough to raise the butt the desired height 
of bridge. Float down stream, butt end first, to position of bridge. 
On arriving in line of bridge, the log is turned on its feet, the tip 
sinking to bottom. The brace leg is then inserted down stream 
in last hole, making an angle of 45°. Log after log is thus placed, 
balks rolled up and put into position and leveled, and the floor laid 
in the usual way. 

261. —Trestle Bridges. For spans of 25 ft. or over, when bot- 
tom can be touched clear across, some form of trestle bridge will be 
the easiest of construction. 

262.— The Six-legged Trestle. In PL 36, Fig. 1, the trestle con- 
sists of 6 legs, 4 vertical and 2 inclined; the two vertical legs on 
each side are fastened to two short sills by 2-in. pins. The ends of 
the two inclined legs are cut on an angle, driven into position, and 
held by 2-in. pins passing through the transom from above. They 
serve as braces and supports. A short horizontal piece pinned to 
each pair of vertical legs supports the transom, which is also 
pinned. On top of the projecting ends of the vertical legs a cap 
piece can be pinned to form hand-rails. The trestle is made on 
shore, floated to its place in bridge, and erected with the aid of a 
float held at the proper distance from last trestle by a pole, on each 
side, having the lengths of the spans marked by pins which engage 
the transoms of the trestles. The transoms are only temporarily 
lashed in position at first, but after the trestle is erected in its 






Spar Bridges. 125 

propel- piace the proper height for it is determined by bringing 
the 2 distance poles horizontal, or a little above the horizontal if 
a camber is to be given, then pinning or spiking on the short hori- 
zontal pieces. If accurate soundings have been made across the 
stream on the lines of the legs of the trestles, then the trestles can 
be completed on shore before launching. The balks are then 
run across and pinned and roadway finished. If there occurs 
unequal settling, the roadway can be raised by blocking up under 
the transoms on the short horizontal pieces. 

263.— The Tie-block Trestle. Fig. 2 is another form of tres- 
tle, consisting of only two legs, about 8 in. in diameter. 
The transoms are in pairs, across which two blocks are spiked at 
each end into notches, as shown. This trestle can be used on 
hard, uneven bottom. The trestle is formed on shore, held in 
shape by the rope, and rack stick across the top, then floated into 
place. Two poles, longer than two spans, are then run out; on the 
projecting ends are pins to prevent the trestle slipping off, and on 
near end a rope for fastening to transoms of second trestle back. 
Having caught the trestle on the ends of the poles under the 
transom, it can be raised to a vertical position by men bearing 
down on the rear, and held by means of ropes; it is then lowered 
into position, legs in a vertical plane. The transoms are then 
adjusted to their proper elevation by striking on under side, if 
too low, then tightening rope; or by slackening the rope and strik- 
ing on upper side if too high. When properly adjusted, the rope is 
tightened, pinching the legs between the blocks; the braces are 
then spiked or pinned on, the rope removed, the balks laid and 
pinned, and the poles shoved out for the next trestle. 

264, — The Four-legged Capped Trestle. Where sufficient lum- 
ber can be procured, the most expeditious and probably the best 
method will he as follows: (Pig. 3.) With the balks and chesses 
for each span, form a raft, or as many as may be desired, the length 
of a span. Form a trestle by placing four legs parallel and 4 ft. 
apart from center to center. Spike a pole across near the bottom 
and one near the top to keep them together. The first, or any tres- 
tle, having been set, float a raft against it and make fast; bring the 
trestle to be set up to the other end; force the legs under the raft a 
distance a little less than the depth of the water. Tie a rope around 
the outside legs at "f" with a bow-knot, to hold from slipping un- 



126 Spar Bridges. 

der, and others to the top pole, by means of which it is raised to a 
vertical position, when it is dropped to the bottom by slackening 
off on lower ropes. As soon as it is dropped,another raft is brought 
up, tied, and another trestle put into position, and so continued. 
Each trestle, as soon as it is in position, is then capped by nailing 
two boards horizontally on opposite sides of legs with tops in same 
plane. (Fig. 3, a.) Braces are. then spiked on the legs. Saw -off the 
two inside posts even with the tops of boards. Spike a 2-in. plank 
across the top of posts and boards. Lay the balks, spike them, 
remove the raft, and move it into position to raise another trestle. 
If boards cannot be procured for capping, round sticks may be 
used as in Fig. 3, b, by cutting the two inside legs off 5 or 6 in. 
above the horizontal poles, then spiking two short pieces across 
the poles against the outside legs and one in center on which the 
cap piece or transom will rest. Advantages are— work can be 
commenced in any number of places at the same time; no accu- 
rate soundings required so long as poles are sufficiently long; cap- 
ping and bracing do not retard work; different squads can be at 
work at same time, etc. 

265 — The Two-legged Trestle'. If only axes and rope are 
available, trestles may be made by lashing their parts together. 
(Fig. 4.) Having determined the height of the roadway above 
the bottom of the stream, mark this height from the butts on 
both legs, then mark the position of the transom on the legs, 
allowing for the thickness of the balks; also mark on the transom 
the width of roadway between side-rails plus 3 ft., for points 
of crossing of legs, the distance apart of legs depending on 
width of roadway. Give the legs a splay outwards at the bottom 
of 1-6 and mark on legs and ledger the points of lashing. All be- 
ing ready, lay the transom on a couple of supports 3 or 4 in. high, 
inside the position of the legs, lay on the legs in their proper posi- 
tions, on the legs lay the ledger. With the square lashing fasten 
the four points of crossing. Next, lay on the braces, butts and 
one tip on same side as ledger and one tip on side of transom. 
Lash the butts with square lashings. Square the trestle by mak- 
ing the diagonals equal, measuring from the center of ledger lash- 
ing on one leg to the center of transom lashing on opposite leg. 
When these diagonals are made equal the tips are lashed with 
square lashings and the braces at the middle with a cross lash- 



Spar Bridges. 127 

iiig. Ledger and braces can be of rather light timber. The tres- 
tles can be floated into position and raised as already described, 
or run out and down from the end of the bridge, which is more 
difficult. They are kept vertical by lashing the balks to the 
transoms, and longitudinal bracing from one to another. 

266.— A Three-legged Trestle (PL 37, Fig. 1) may be made 
by first lashing two legs together considerably higher than the 
roadway is to be, then lashing the pry -pole just below to one of 
the legs, all with shear lashings. Stand the trestle up, spread 
out legs till butts rest on the vertices of an equilateral triangle 
whose sides are % height of trestle, then lash three light ledgers 
to the legs by round lashings. On the outside of the pry-pole 
and leg to which it is fastened are lashed short pieces, by square 
lashings, on which rest two longer pieces, separated by the legs, 
which are lashed together by the shear lashing. On these longer 
pieces rest the transoms. With these trestles lighter material 
can be used; they stand without bracing, but are difficult to place; 
accommodate themselves to inequalities of surface; the roadway 
may be readily raised or lowered. If material is available, they 
are readily made with spikes. 

267. — The Four-legged Trestle, second form. (Fig. 2.) Two 
two-legged trestles are mtade, one being 12 to 18 in. narrower than 
the other, depending on the size of legs, so that they will lock when 
put together. The transoms are placed on same side as ledgers, 
instead of on opposite sides. The butts of the single trestles are 
placed a distance apart equal to half the height, then locked at 
the top, the transoms lashed at the ends, longitudinal braces 
lashed at the ledgers, the tips tied and racked together. Some- 
times used with light material, also as steadying points in a long 
bridge of two-legged trestles. One similar to it can be made of 
sawed timber and spikes and placed in position as shown in Figs. 
3 and 4, if the materials are available. 

26S. — Crib Piers. In sluggish streams with muddy bottoms and 
not over 6 ft. deep, where timber is abundant, crib piers may be 
used. (Fig. 5.) The. cribs are built in the woods, the foundation 
logs being pinned together, the others simply notched. The logs 
then marked, taken down, carried or floated into position, and re- 
built, poles being generally set to mark the corners. As the crib 
is built up it gradually sinks, or a tray may be formed inside and 
loaded with stones. The balks and flooring are laid as usual. 

9 



PLATE 37. 




FLATE 38. 



FIG. 1. 




FIG. 4. Single Lock 




jmJ 



130 Spar Bridges. 

269.— Pile bridges are scarcely adapted to an emergency, from 
the time and preparation required in their construction, but on 
lines of communication, from the character of the bottom or the 
dangers from floating objects, resort may be had to them. 

270.— For driving the piles, a monkey (Fig. 8) is made of a 
block of wood 3 ft. long, 12 in. in diameter, with four 1.5 in. pins 
at top and four on the sides for handles. Four men standing on 
a platform on the pile drive it down, their own weight thus assist- 
ing, or they may be driven from a raft built as in Fig. 6. After 
the piles are driven they are straightened, braced, their tops sawed 
off level, the caps placed on and pinned (PL 38, Fig. 1), and the 
roadway laid as usual. Piles near shore may be driven as in Fig. 7. 

271.— For crossings greater than 25 ft. and too deep to use any 
of the above forms, resort must be had to some form of truss 
bridge. The trusses may be put together either by lashing or 
with pins, or by combinations of both. 

272. — PI. 38, Fig. 2, represents the ordinary King-post Truss 
for spans up to 40 ft. The bridge is put together on the bank, 
then pushed forward half its length, using rollers under each 
truss, as shown. A trestle is then leaned forward from opposite 
bank, and, when truss is over it, the trestle is raised and the end 
of the truss carried over to the opposite bank. 

273.— Fig. 3 represents the Queen-post Truss for spans up 
to 50 ft. It is constructed and carried across similarly to the pre- 
ceding one. 

274.— Fig. 4 shows the Single Lock for spans of 30 ft. It con- 
sists of two frames similar to the two-legged trestle on PI. 36, 
Fig. 4. A section of the gap is first marked out on the ground on 
each bank with the positions of the footings indicated. On these 
the legs are laid and the positions for lashing the transoms and 
ledgers marked. The frames are then put together opposite the 
position they are to occupy (one on each bank), butts towards the 
gap. One frame is made 15 to 18 in. wider than the other so they 
will lock, and the footings should be likewise prepared. The dis- 
tance between legs at transom of narrower frame is at least 18 in. 
more than width of roadway between side-rails. With the above 
exceptions, the frames are made like the two-legged trestles. The 
splay of the legs is very slight, generally about 1 ft. between tran- 
som an 1 ledger. Stout stakes are then driven at the rear, fore and 



Spar Bridges. 131 

back guys are attached to the tips of each frame, the fore guys 
crossed over the stream, those of narrower frame in center. Foot 
ropes are also attached to each leg near the butts with timber 
hitches and a turn taken around the stakes at the rear. The frames 
are then shoved over the banks till they balance (PI. 40, Fig. 1), 
then brought to a vertical position by hauling on the fore guys, 
and lowered into their places by easing off on the foot x'opes, 
after which they are pulled over and locked. A couple of balks 
are then run out, then the fork transom is put into place and the 
balks rested on it. The remainder of the balks are then run out, 
placed on the fork transom, lashed, and the roadway completed 
as usual. If good places for footings cannot be secured, then 
other means must be provided. 

275.— For spans up to 45 or 50 ft., the Double Lock (PL 39, 
Fig. 1) may be used. In this it will be noticed that the balk- 
bearing transoms are not the transoms first lashed to the frames 
la making them, but those which are sent out after the frames 
are in position. This must be remembered in marking the posi- 
tions of the transoms on the legs of the frames. In this the 
two frames are made as described for the single lock, except that 
they are of the same width. They are launched as described, 
and pulled forward until their tops are about 1-3 the span apart. 
Two straining beams are then run across, the road-bearing tran- 
soms fastened on top of them in the positions previously marked. 
The frames are held by the back guys until all is ready, when 
they are eased off and the bridge locked. The roadway is then 
laid as usual. 

276.— For spans greater than 45 or 50 ft., where timber of suffi- 
cient size is obtainable, the Single Sling or Treble Sling may be 
used. The frames are made as has been described, with the .fol- 
lowing additional observations: 

In the Single Sling (Fig. 2), in marking the positions of the dif- 
ferent spans, the three locking pieces must be at least 9 or 10 ft. 
above the roadway. The fork piece is hauled into position by 
snatch blocks lashed to the top of each leg of narrower frame, 
after which the blocks are used to get the center transom tempo- 
rarily into position, when it is slung by the ropes that are to hold 
it, by taking several turns around it and the locking pieces with- 
out riding, and afterwards twisted up to the proper height with 
a pole. 



PLATE 39. 



Double Lock, 




Fig. 3 



M!L 



PLATE 40. 




134 Spar Bridges. 

277.— In the Treble Sling (Fig. 3) there are three slung tran- 
soms, one from the forks and one from the standards on each side 
of the middle. The frames are constructed as already described, 
(PL 40, Fig. 2, being one in plan.) If necessary, the frames may 
be strengthened by additional braces on them and further braced 
back to the banks by ropes attached to holdfasts and otherwise 
as suggested on PL 40, Figs. 4 and 5, vertical braces being shown 
in Fig. 3. 

278.— Other expedients for crossing small gaps are the use of 
wagons in various ways for supports, brushwood made into 
gabions, fascines, etc. (Figs. 6 and 7.) 

279.— A light, portable truss (Fig. 11) can be made, where 
boards are obtainable, by describing two arcs of circles with 
radii 151 ft., on opposite sides of a 60 ft. chord, then driving 
stakes on the arcs at intervals of about 2 ft., against which 5 
layers on top and 6 layers on bottom of boards 1 in. thick x 12 
in. wide, breaking joints, are bent and securely nailed together 
every 4 in. with tenpenny nails. The lower side of truss is made 
one board thicker than the upper and is completed by driving 
6 in. spikes through every 6 in. This truss will be about 6 ft. 
deep, and, allowing 2 ft. at each end for resting on supports, will 
bridge a span 56 ft. 

The sides are connected every 5 or 6 ft. by vertical pieces of 
plank and two 1-in. iron rods, the latter on the sides of the verti- 
cals, towards the middle. If iron rods are not obtainable, rope or 
wire should be wrapped around both and twisted tightly. The 
angles at the ends are filled with wedge-shaped pieces and the 
ends securely bolted, hooped, or wrapped. (Fig. 9.) For greater 
rigidity, light diagonal braces may be inserted in the panels. 
The top can be made straight instead of curved if so desired. 

These trusses are used in pairs and are applicable to a variety 
of structures and to spaces of considerable width. Two such 
trusses with a central support of trestles, crib- work, or boats, may 
be used for 116 ft. (Fig. 11): three such trusses for 176 ft., etc. 
In experiments with such trusses in bridges, 1800 lbs. per lineal 
foot has been applied before breaking; and by covering the boards 
with pitch and tar before nailing together, inserting V 2 in. bolts 
in pairs every foot of length on lower side, and nailing boards 
against the edges, 3500 lbs. per lineal foot was applied before 
breaking. 



Spar Bridges. 135 

280.— Suspension Bridges. For spans greater than- GO ft.., 
a ud when timbers for frames cannot be procured, some form ot 
suspension bridge might be used. Although applicable to longer 
spans, and the materials more easily transported, they take longer 
to make than other kinds. 

The cables may be of iron chaius, iron, steel or fibrous ropes, 
or of boards nailed together. 

281.— PL 40a, Fig. 1, shows one with the roadway hung below 
the cables, with a camber 1-30. At the center, the roadway 
should be at least 1 ft. below the cables. The width of roadway 
between side rails should be only slightly wider than wagon-wheel 
tracks. (Fig. 2.) On the banks, the cables are supported by tim- 
ber piers (Fig. 3), having a broad cap (Fig. 4), rounded on top, 
over which they pass at a distance apart of 9.5 ft. The cables 
must be securely anchored at the rear to heavy logs sunk 4 or 5 
ft. in the ground, or otherwise, and drawn in until the sag is only 
1-10 or 1-12 of the span. 

282.— In Fig. 5, part of the roadway is hung below and a part 
rests on the cables, the greatest slope of road being 1 on 6 for 100 
ft. span and 1-10 sag. The cables are only 7 ft. apart. 

283.— In Fig. 6, the roadway is built on trestles supported on 
the cables. For spans 130 ft. sag 1-12, the frames form the sides 
of equilateral triangles of 10 ft. each. To construct it, the curve 
of the cables is traced on the ground, the trestle legs laid on it and 
marked where they cross the road and cable; those for each half 
of the bridge are ranged in order on the banks, connected together 
as placed on the cables and hauled out, connected at the center, 
the curve of the cables adjusted and the bridge completed. 

284.— Fig. 7 is a suspension bridge of which the cables are 
made of boards nailed together in several thicknesses laid hori- 
zontally, breaking joints; the ends are spread apart and wedge- 
shaped blocks inserted and anchored by several rows of posts, as 
shown in Fig. 8. Each cable, as made, is drawn across by ropes, 
anchored, and the trestles placed from both ends at the same 
time. Last of all, spikes long enough to reach entirely through 
the cable are driven every 4 to 6 in. 

285.— Fig. 11 is a similar bridge supported on trestles 16 ft. 
long, not exceeding 20 ft. high, placed at intervals of 40 ft., over 
which suspends the two board cables, 14 ft. apart. On these are 



PLATE 40a. 




Pig.6. 




Pig. 10. 



,i.i . . . i a,h i . m m . iiip vWi up pi^ui'."i|...<L .."I.U 






Spar Bridges. 137 

placed low trestles, 3 ft. high, dividing the spans into lengths of 
20 ft. each; 25 ft. balks are used and the roadway laid as usual. 
The cables are made of six thicknesses, of 1 in. boards 12 in. 
wide, breaking joints, nailed and spiked every 4 to 6 in., and bolt- 
ed by pairs of % in. bolts every foot. Three thicknesses of boards 
are first nailed together and drawn across, the ends anchored, and 
then the other three boards added. 

286.— For light foot bridges (Fig. 10), across narrow gaps, wire 
from fences, if available, could be used for the cables by twisting 
a number together and passing them over crotches of trees and 
anchoring to stumps, etc., in rear, and then laying the walk simi- 
lar to some of the methods previously shown. 

287.— So various are the conditions to be met in constructing 
bridges that seldom will any one type meet the requirements, but 
by the application of good judgment and resource, with the sug- 
gestions here offered, almost any gap of reasonable width may be 
crossed, if not by one type or another, then by a combination of 
several to meet the emergency. 

The varying strength of timbers makes it almost impossible to 
give exact dimensions for the different spars to be used in the 
different types, but a general idea may be obtained below of the 
amounts and average dimensions of medium strength timber, as 
yellow pine. For weaker timbers some of the sizes will have to 
be increased, while for stronger ones there will be an excess of 
strength if the sizes given are adhered to. but the desire to be on 
the side of safety warrants the use of amounts which might, by a 
careful mathematical calculation, appear to be excessive. 

The timbers for transoms, ledgers, braces, balks, flooring and 
side rails should be selected of as nearly a uniform diameter 
throughout as possible and will be so considered in giving dimen- 
sions. For legs or standards the diameter at tip will be given. 

For a 9 ft. roadway with 15 ft. spans. 5 balks 20 ft. long x about 
6 in. in diam. are used, and placed 2V 4 ft. apart from renter to cen- 
ter. For the flooring are used poles 11 to 12 ft. long x 4 to 5 in. 
in diam. For side rails 2 poles 20 ft. long, 4 to 6 in. in diam. 

Tor each Six-legged Trestle (PI. 3fi. Fig. 1) 4 vertical and 2 
bracing legs G in. diam.: 1 transom 12 ft. x 8 in.: 2 foot pieces 3 ft. 
x 8 in.: 10 oak pins 2 in. diam. 

For each Tie-block Trestle (Fig. 2) 2 legs 8 in. diam.: 2 tran- 



138 Spar Bridges. 

soms 15 ft. x 8 in.; 4 tie blocks 2 ft. x 5 in. x 6 in.; 2 braces 3 ft. x 

2 in. x 6 in.; 24 spikes, 1 rope, 1 rackstick. 

For each Capped Trestle (Fig. 3) 4 legs 8 in. diam.; 2 braces 
12 ft. x 4 in.; 2 braces 15 ft. x 5 in.; 3 boards 12 ft. x 2 in. x 12 in.; 
4 ropes, spikes. 

For each. Two-legged Trestle, lashed (Fig. 4), 2 legs 4 ft. 
longer than height of trestle, 5 to 7 in. tip; 1 transom 15 ft. x 9 in.; 

1 ledger 16 ft. x 4 to G in.; 2 braces 3 to 5 in. diam.; 6 ropes 30 ft. x 
y 2 in. diam.; 3 ropes 15 ft. x V 2 in. diam. 

For each Three-legged Trestle, lashed (PI. 37, Fig. 1), 6 legs 3 
to 5 in. tip; 4 transom bearers 6 ft. x 3 to 4 in.; 4 sticks 2 ft. x 2 to 

3 in.; ledgers 2 to 3 in. diam.; 1 transom 15 ft. x 9 in.; 12 ropes 
30 ft. x V 2 in. diam.; G ropes 15 ft. x V 2 in. diam. 

For each Four-legged Trestle, lashed (Fig. 2), twice the 
amount given for each two-legged trestle, plus 2 ledgers, and 6 
lashings 15 ft. long. 

For each Single Lock (PL 38, Fig. 4) 4 legs 22 to 25 ft. x 7 
in. tip; 1 fork transom 15 ft. x 10 in.; 2 frame transoms 15 ft. x 6 
in.; 2 ledgers 15 ft. x 4 to 6 in.; 4 braces 20 ft. x S in.; 2 shore sills 
15 ft. x 6 in. Lashings, 4 transom 50 ft. x % in.; 14 ledger and 
brace 30 ft. x y 2 in.; 10 balks 20 ft. x 1-3 in.; 4 foot 50 ft. x 1 in.; 8 
guy 150 ft. x 1 in. 

For each Double Lock (PL 30, Fig. 1) 4 legs 22 to 25 ft. x 7 in. 
tip; 2 straining beams 25 ft. x 8 in.; 2 road transoms 15 ft. x 10 in.; 

2 frame transoms 15 ft. x 6 in.; 2 ledgers 15 ft. x 5 to 6 in.; 4 
braces 20 ft. x 3 in.; 2 shore sills 15 ft. x 6 in. Lashings, 8 transom 
50 ft. x % in.; 14 ledger and brace 30 ft. x % in..; 10 balk 20 ft. x 
1-3 in.; 4 foot 50 ft. x 1 in.; 8 guy 150 ft. x 1 in.; besides axes and 
other tools, and anchorages, holdfasts, etc., on banks. 

For each Single Sling (Fig. 2) 4 legs 35 to 45 ft. x 6 in. tip; 

3 top and fork transoms 15 ft. x 6 in.; 3 road transoms 15 ft. x 10 
in.; 2 ledgers 15 ft. x 4 to 6 in.; 4 braces 20 ft. x 3 in.; 2 shore sills 
15 ft. x 6 in.; 10 balks 30 ft. x 6 in.; 4 side rails 30 ft. x 4 to 6 in. 
Lashings of same number, size and length as for Double Lock. 
Stiffening will require additional spars and lashings, depending 
upon the method used. 

For each Treble Sling (Fig. 3) 4 legs 50 ft. x 6 in. tip; 5 road 
transoms 15 ft. x 10 in.; 3 top and fork transoms 15 ft. x 6 in.; 2 



Spar Bridges. 139 

lower ledgers 15 ft. x 4 to 6 in.; 4 lower braces 20 ft. x 3 in.; 4 upper 
braces 18 ft. x 3 in.; 2 shore sills 15 ft. x 6 in.; 15 balks 5 ft. longer 
than 1-3 span x in.; 6 side rails 5 ft. longer than 1-3 span x 4 to 
G in.; G sling racking sticks 10 ft. x 4 in. Lashings, 4 foot 50 ft. 
x 1 in.; 8 guy 150 ft. x 1 in.; 24 ledger and brace 30 ft. x y 2 in.; 
8 transom 50 ft. x % in.; 40 or 50 balk 20 ft. x 1-3 in. Stiffening 
will require additional spars and lashings, depending upon the 
method used. 

For Suspension Bridge 200 ft. long (PI. 40a, Fig. 1) 4 to 8 ca- 
bles 180 ft. x 1 in.; 16 cable seizings of yarn 18 ft. long; 12 lash- 
ings 50 ft. x 2-3 in.; 10 lashings 30 ft. x % in.; 100 lashings 20 ft. 
x 1-3 in.; 2 steel wire cables 400 ft. x 1 2-3 in.; 4 standards 26 ft. x 
10 in. tip; 4 braces 22 ft. x 3% in. tip; 2 caps 12 ft. x 10 in.; 2 sills 

15 ft. x 10 in.; 4 back struts 36 ft. x 4 in. tip; 4 side struts 32 ft. x 
3 in. tip; 4 cable props 30 ft. x 5 in. tip; 4 horizontal ties 30 ft. x 
3 in. tip; 21 transoms 10 ft. x 6 in.; 80 balks 13 ft. x 6 in.; 40 side 
rails 20 ft. x 6 in.; for anchorages 16 spars 5 ft. x 7 in. tip; 2 spars 

16 ft. x 20 in.; 2 spars 16 ft. x 12 in. % round; 10 spars 16 ft. x 8 
in. % round; 4 back ties 50 ft. x 2-3 in. steel rope; 4 ties 35 ft. x y 2 
in. steel rope; 40 slings total 600 ft. x y 2 in. steel rope; 4 guys 50 
ft. x 1 in.; 4 rope ladders. 

For Suspension Bridge 100 ft. long (Fig. 5) 4 to 8 cables, 12 
cable seizings, 4 lashings, 12 lashings, 30 lashings as above; 2 
cables 180 ft. x 3 in. hemp or 2 in. steel ; 2 anchor spars 18 ft. x 15 
in.; 10 transoms 12 ft. x 4 in.; 4 balks 25 ft. x 6 in.; 10 side rails 20 
ft. x 4 in.; materials for piers depending on circumstances. 

For Suspension Bridge 130 ft. long (Fig. 6) 4 to 8 cables, 12 
cable seizings, 9 lashings, 104 lashings, 280 lashings as above: 1 
cables 200 ft. x 2 2-3 in. hemp or iy 2 in. steel; 2 anchor spars 18 ft. x 
18 in.; 44 trestle legs 13 ft. x 3 in. tip: 44 braces 15 ft. x 2 in. tip: 22 
transoms 9 ft. x 4 in.; 80 ledgers 12 ft. x 2 in.; 20 cable ledgers 12 
ft. x 5 in.; 2 shore sills 10 ft. x 5 in.; 48 balks 14 ft. x 5 in.; 28 side 
rails 20 ft. x 5 in.; materials for piers depending on circumstances. 

Besides the above materials, there will be required tools for 
cutting timber, tackles for raising frames, shovels, pickets, etc., 
and, where not mentioned, the ordinary amounts of balks, chess, 
side rails, etc. 



CHAPTER XVI.-FIoating Bridges. 

288.— The passage of a stream may be effected, in many cases, 
as described in the preceding chapter. If the methods there laid 
down are not suitable or expedient, and the stream cannot be 
forded, then resort must be had to ferrying by boats, rafts, flying 
bridges, or to floating bridges. 

289.— The selection of a place and means of crossing a river 
is determined by a reconnaissance, which should be as detailed 
and extensive as circumstances will permit, and embrace the 
following:— 

(a) The nature of the banks. 

(h) The nature of the bed. 

(c) Position and depth of fords. 

(d) Strength of the current. 

(e) Whether tidal or otherwise. 

(f) Probability and extent of floods. 

290.— Fords. A stream with a moderate current may be 
forded by infantry when its depth does not exceed 3 ft., and by 
cavalry and carriages when its depth is about 4 ft. The requi- 
sites of a good ford are: — 

(a) Banks low, but not marshy. 

(h) Water attaining its depth gradually. 

(c) Current moderate. 

(d) Stream not subject to freshets. 

(e) Bottom even, hard, and tenacious. 

291.— In a mountainous country, the bed of a stream is likely 
to be covered with large stones, rendering the passage of car- 
riages impracticable. In level countries, the bed of the stream 
may be composed of mud or quicksand, rendering passage by 
fording impossible. In some cases, the bottom is composed of 
fine sand, which is hard enough, but which, by the action of the 
hoofs of the animals, is stirred up; the current then carries the 
sand away and the ford is deepened, perhaps so much as to be- 
come unfordable. The best bottom is coarse gravel. 

292.— Fords are usually found in the wider and more rapid 
parts of a stream. A straight reach gives the most uniform 
depth. At bends, the depth will generally be greater at the con- 
cave bank and less at the convex. (PI. 41, Figs. 1 and 3.) 



PLATE 41. 




142 Floating Bridges. 

293.— To determine the position of a ford:— 

(1) A number of mounted men may be sent across wherever 
there is a probability of the river being shallow enough. 

(2) Most certain method. Float down the stream in a boat, 
keeping in the swiftest part of the current, where the water is 
usually deepest. Hang a sounding line of the proper length over 
the stern. When this touches bottom, sound across the stream. 

When a ford is discovered, it should be marked by stakes; re- 
markable objects on the shore should be noted; and a stake 
planted at the water's edge and marked, in order that any rise 
in the water may be at once evident. 

294.— A stream, otherwise unfordable, may be passed:— 

(1) By crossing it in a slanting direction. (Fig. 2.) 

(2) When the unfordable portion is not over 8 or 10 yards, this 
may be filled in with fascines loaded with stones. (Fig. 4.) 

(3) When the bottom is muddy, it may be covered with bun- 
dles of coarse grass, rushes, or twigs, sunk by means of stones. 

(4) A portion of the water may be diverted from its natural 
channel. (Fig. 5.) 

295.— In passing a stream by fording, if it is deep and the cur- 
rent at all swift, the following precautions should be taken: — 

(a) Troops passing in column should do so at a considerable 
interval, in order to avoid choking the stream. 

(b) If boats are to be had, a few should be stationed below the 
ford, to assist men who may be carried down by the current. 

(c) If boats cannot be procured, mounted men may perform 
the duties described in the foregoing provision. 

(d) In place of provisions "b" and "c," a life line, held up by 
casks, may be stretched across the stream. 

(e) In order to break the force of the current, cavalry may be 
stationed in the stream, above the point of crossing. 

296.— After a freshet, a ford should always be reexamined, 
lest some alteration may have taken place in the bed of the 
stream. The banks of a stream to be forded should, if necessary, 
be cut down. 

The velocity of a stream may be determined by throwing in a 
light rod, so weighted as to stand vertically. Note the distance 
passed over in a certain number of seconds; then, 7-10 the mean 
number of feet per second gives the velocity in miles per hour. 



Floating Bridges. 143 

297.— Ice. In high latitudes, during the winter, rivers are fre- 
quently covered with ice of sufficient thickness to sustain the 
heaviest loads. This means of passing a stream should be used 
with great circumspection. A change of temperature may not 
only suddenly destroy the natural bridge, but render the river 
impassable by any method, for a considerable time, in conse- 
quence of floating ice. 

298.— Ice, in order to allow of passage, should be of the follow- 
ing thickness:— 
For Infantry, single file, 2 yds. distance, on a line of 

planks 2 in. 

For Cavalry or light guns, with intervals . . 4 in. 

Heavy field-pieces 5 to 7 in. 

Heaviest loads 10 in. 

299.— When there is any doubt as to the strength of the ice, 
two tracks of plank may be laid for the carriage wheels to run 
on, or the wagon may be transformed into a kind of sled by fas- 
tening two planks under the wheels. (Fig. 6.) 

The thickness of ice may be increased, when the temperature 
is low, by throwing water on it. When a stream is frozen on each 
side but open in the middle, in consequence of the velocity of the 
current, a boom stretched across the open space will often check 
the velocity sufficiently to allow the water to freeze. 

300.— If a stream cannot be forded, it may be crossed by fer- 
rying or by constructing a bridge. Ferrying may be by boat, 
raft, or flying bridge; rowed, sheered, or hauled across. 

301.— Ferrying by Boat. All boats available should be 
collected and taken to the chosen point of passage. The banks of 
the stream, if steep, should be cut down to facilitate embarkation. 
The landing should be farther down the stream than the point 
of starting. The boats should be arranged along the shore and 
numbered. Entrance to the boats should be by file, the soldiers 
taking positions on opposite sides alternately. Where the water 
is shallow near the shore, the boat should not approach the bank 
so closely as to ground as the men file in. The unloading should 
be made 1n the same manner as the embarkation — i. e., by file 
alternately from each side of the boat. During the transit, the 
men should remain in position and not rise up suddenly when the 
boat lurches. 

In passing artillery, the piece should be dismounted. Horses 
10 



144 Floating Bridges. 

should, ordinarily, be made to swim. However, if the boats are 
large enough, the bottoms may be covered with plank, and the 
horses placed crosswise, facing alternately up and down stream. 

302.— Ferrying by Raft. Rafts may be made of logs, lum- 
ber, casks, and other material suitable for the purpose. Their 
construction is the same as explained for piers of bridges, hence 
only two expedients will be mentioned here. 

303.— The Canvas Raft. No other material being available, 
small rafts can be constructed by the use of canvas about 8 x 
12 ft., and brushwood. Wet the canvas to make it water-proof, 
and lay it out on the ground. Across the width place sticks in 
layers, the longest near the middle. The sides should be strength- 
ened by heavy sticks placed lengthwise. The pile of sticks 
should be about 4 ft. wide in the center and sloping off slightly 
towards the ends, 3 ft. high and 8 ft. long. Over this pile a sec- 
ond piece of canvas, after being wet, should be placed. The 
sides of the canvas on the ground are now drawn over toward 
each other and lashed securely with a lariat. The ends are folded 
neatly, brought up towards each other, and lashed. If care is 
taken to w r et the canvas thoroughly and make it water-tight, this 
raft will carry three troopers with their arms and accouterments. 
By lashing several together, a larger number of men, with their 
arms and accouterments, can be carried. 

304.— Rafts of Skins. Bags, made of the skins of animals, 
inflated with air or stuffed with hay or straw, can be utilized for 
crossing streams, and have been used from ancient times. 

305.— Rafts are more suitable for the embarkation and landing 
of troops of all arms than boats. They will carry a larger num- 
ber each trip, are not so easily injured by the fire of the enemy, 
and draw little water. On the other hand, they cannot be navi- 
gated with the same facility as boats, move much more slowly, 
and hence keep the troops much longer under fire; cannot be 
directed with certainty on a fixed point when the stream is rapid, 
and, if the passage is to be effected secretly, the time required for 
their construction is too long to admit of their use. 

306. — The Floating' Bridge.* This may be formed of two 

*A simple modification of the floating bridge is an expedient used in the Philip- 
pine Islands for floating wagons across deep streams. 

This is merely to run the vehicle into the stream astride of two bancas (narrow 
dugouts), the axles resting on the gunwales and the boats as far apart as the 
hubs of the wheels will allow. Wagons can thus be readily crossed without un- 
loading, provided the bancas are large enough to support the weight. 



Floating Bridges. 



145 



boats covered with a platform, cons true ted as follows:— (PI. 42, 
Fig. 1.— The lashings and side rails are omitted.) From 5 to 7 
beams of the same thickness are laid across the two boats, the 
intervals between the beams being equal, and such that the cover- 
ing planks extend 1 ft. beyond the extreme beams. The interval 
between the boats is such as to allow the beams to extend 2 ft. 
beyond the gunwales. The beams are lashed to the boats, the 
covering planks are kept in place by 2 side rails, laid directly over 
the outer beams, and lashed down to them; the extreme planks 
should be nailed down. 

The floating bridge can be navigated by oars with nearly the 
same facility as a boat. 

307.— The Rope Ferry. The rope ferry, which is used in slug- 
gish streams, consists of a floating support, either a raft, float- 
ing bridge, or a large boat. It is drawn by hand along a rope 
stretched from shore to shore. 

308.— The Trail Bridge. This is employed in streams not 
more than 150 yds. in width, and whose current is not less than 3 
ft. per second, or 2 1-10 miles per hour. The rope must be main- 
tained above the surface of the water, and, consequently, must be 
drawn very tightly by means of a windlass, blocks, and falls, or 
similar expedients; it must, also, at each bank, be raised some dis- 
tance above the water.* (PI. 42, Fig. 3.) 



*a convenient expedient for tightening the rope when no blocks are at hand is 
here shown. 




Another rope "r" is attached to the ferry rope "R" at "a" by a stopper hitch and 
then passed round the holdfast and through a loop "b" in the ferry rope: power is 
then applied as indicated by the arrow, the slack of the ferry rope being taken in 
at "c." When the ferry rope is taut enough the attached rope "r" is eased off 
thus letting the strain come gradually upon the cable again. 



PLATE 42. 



Fig.l. 



Pig. 2. 




PLATE 43. 




148 Floating Bridges. 

The raft, or boat, is attached to a pulley, which runs on a sheer 
line, and by means of a rudder is given such a position that its 
side makes an angle of about 55° with the direction of the cur- 
rent. The angle of 55° with the current divides its force against 
the side of the boat into two components: one, perpendicular to 
the sheer line, which is counteracted by the resistance of this 
line; the other, parallel to it, which moves the boat. A boat for 
this kind of ferry should be narrow and deep, with nearly ver- 
tical sides. 

If a raft is used, it should be lozenge-shaped, the acute angle 
being about 55°. When two sides are parallel to the current, the 
up-stream side will then be in the most favorable position for 
passage. (PL 43, Fig. 8.) 

309.— The Flying Bridge. The character of the float for 
this ferry is the same as in the preceding case. (PL 41, Fig. 7; 
PL 42, Fig. 2.) This bridge is resorted to when the stream is 
wider than 150 yds. The strain on the sheer line being very 
groat, it is replaced by a cable anchored in mid-stream, in which 
case the float would swing between two landing piers; or by two 
cables, one anchored on either bank, the float swinging between 
four piers. The latter requires less skill in manipulation. The 
angle which the float makes with the current is the same as that 
of the "trail" bridge. A sharp bend may be utilized for anchor- 
ing the cable, as shown in PL 42. Fig. 4. 

The length of a swinging cable should be 1% to 2 times the 
width of the stream. The cable should be supported on inter- 
mediate buoys or floats, to prevent it dragging in the water. 

310.— Floating Bridges are composed of a roadway and its 
supports. The roadway is explained in the preceding chapter. 
The supports are floating, as pontons, boats of commerce, rafts 
of barrels, logs, lumber, inflated skins of animals, or other mate- 
rial. The supports are called floatinp piers. It is from the char- 
acter of the support that the bridge derives its name. 

311.— In constructing a floating bridge, the site should be first 
selected and the width of the stream measured. 

In selecting a site, the following points should be noted:— 

(a) Proximity to a road. As the approaches to floating 
bridges, having frequently to be constructed across meadows, give 



Floating Bridges. 149 

much trouble, they should be as short as possible. For a similar 
reason, marshy banks are undesirable. 

(b) The bed of the stream, if anchors are required, should 
afford good holding ground. 

(c) A bridge can be best defended if constructed at a reenter- 
ing bend of a river. 

(d) Use can frequently be made of islands to economize 
material. 

312.— In measuring the width of the stream, if it cannot be 
done directly, some one of the methods explained in Chap. III. 
can be used. 

313.— It should be remembered that a wide roadway gives 
greater steadiness than a narrow one. In making calculations 
for buoyancy, the weight of a 9 ft. roadway may be taken at 80 
lbs. per running foot. 

314.— Piers. Of whatever material the floating pier is made, 
the following points should be observed:— 

(1) The available buoyancy of each pier should be sufficient to 
support the heaviest load that can be brought on one bay of the 
bridge. 

(2) Piers should be connected with each other, at their extremi- 
ties, by tie balks or lashings. 

(3) To insure steadiness, the length of a pier should be at least 
twice the width of the roadway. 

(4) The water way between piers should, if possible, be more 
than the width of two piers, never less. 

315.— Piers of open boats. In forming a pier of open boats, 
the following precautions should be taken:— 

(1) The boat should not be immersed deeper than within 1 ft. 
of the gunwale. 

1 2) If the water is rough, or the current extremely swift, a 
boat should not be immersed deeper than within 1 ft. 4 in. of the 
gunwale. 

(3) Boats should be placed in bridfje with bows up stream or 
toward the current. 

(4) If the stream is tidal, the bows of the boats should be alter- 
nately up and down stream. 

(5) Unless the boat is very heavy and strong, the balks should 



150 .Floating Bridges. 

not rest on the gunwales; a central transom should be impro- 
vised by resting a timber on the thwarts, or seats, blocking up 
from underneath and bringing the weight directly on the keel- 
son. (PL 43, Figs. 6 and 7.) 

(0) Large boats should be placed where the current is swiftest, 
also as the first and last boats in bridge. 

316.— The buoyancy of a boat may be found by one of the 
following rules:— 

(1) To find the available buoyancy load the boat with unarmed 
men to a safe depth. Multiply the number of men thus loaded by 
160. The result will be the available buoyancy in pounds. 

(2) If the boat is afloat and empty, the available buoyancy may 
be found by calculating the volume between the then water line 
and the "safe load" line, and multiplying by 62%. 

(3) To find the total buoyancy. If the boat is of nearly uni- 
form section, the area of the section multiplied by the length of 
the boat will give the cubic contents. A cubic foot of water 
weighs 02% pounds. 

Hence, if the dimensions of a boat are taken in feet, the con- 
tents will be cubic feet, and this, multiplied by 02V2. will give the 
displacement of the boat: from this subtract the weight of the 
boat: this will give the total buoyancy. 

317.— To find the length of a bay. First find the avail- 
able buoyancy of the boat. Then find the weight per running 
foot of the load the bridge is to bear, and to this add the weight 
per running foot of the roadway. Divide the available buoyancy 
by this sum. The quotient will be the distance in feet from center 
to center that boats should be placed apart. Thus: — Suppose the 
weight per running foot is 480 lbs., that the roadway is 80 lbs. 
per running foot. .\ 480+80—500. The available buoyancy is 
found by one of the preceding rules to be 5,(!00 lbs. .*. 5,000 -;- 
560=10, the distance in feet between centers of boats. 

318.— The open boats may be:— (1) Those of commerce usually 
found on streams. (2) Regularly constructed pontons. (3) Im- 
provised boats. 

The first class requires no description. The second class com- 
prises the canvas ponton used in the Advance Guard Train, and 
the boat or barge used in the Reserve Train, of the U. S, 



Floating Bridges. 



151 



319.— The table below gives the dimensions of the ponton in 
the U. S. Advance Guard Train, shown in PL 47. 
Canvas Ponton 21' x 5' 4" x 2' 4". Weight, 510 lbs. 
Balks 22' x 4%" x 4%". 
Side Rails same as Balks. 
Chess 11' x 12" x 1%". 

WEIGHTS FOR ADVANCE GUARD TRAIN. 



Wagon. 


Load. 


Total. 


Ponton 


lbs. 

1,750 
1,750 
1,750 
1,700 
1,217 


lbs. 
1,985 
1,856 
2,060 
1,938 
1,166 


lbs. 
3,735 


Chess 


3,606 


Trestle 


3,810 


Tool 


3,638 


Forge 


2,38c 







320.— The table below gives the dimensions of the ponton in 
the U. S. Reserve Train, shown in PL 48. 

Ponton 31' x 5' 8" x 2' 7". Weight, 1,G00 lbs. 
Balks 27' x 5" x 5" for a 20' span. 
Trestle Balks 21' 8" x 5" x 5". 
Chess 13' x 12" x 1%". 
Side Rails same as Balks. 

WEIGHTS FOR RESERVE TRAIN. 





Wagon. 


IvOad. 


Total. 


Ponton 


lbs. 
2,200 
1,750 
2,200 
1,700 
2,217 


lbs. 
2,900 

2,280 
2,635 
2.100 
1,166 


lbs. 
5,100 


Chess 


4,030 
4,835 


Trestle 


Tool 


3,800 


Forge 


3,383 







321.— Improvised Boats. To reduce the amount of transpor- 
tation required by an army is a very important consideration; 
hence the value of the following expedients. 

322.— The Crib Ponton. This boat is 18 ft. long, 5 ft. wide, 
2% ft. deep and covered with canvas. Construction. (1) Let 
stakes 4 ft. long, 2% in. in diameter, and 2 ft. apart, be driven into 
the ground (PL 44, Figs. 1, 2 and 3), to the depth of about 1 ft., so 
as to enclose a space of the proper size for the top of the boat. 



PLATE 44. 



Fig 1, 




Pig. 2 

^ Hilllil ' 1111 Hi lUiLi'i.'iTIIUIVi^m^ ^ 



Fig. 3. 
I I I I— L 



Fig.6. 




Fig. 7 




J^M^m 



iiiiiiiiiiiiiiiiiiiiiiiiiiiiim^ 



Floating Bridges. 153 

The tops of the stakes should be in the same horizontal plane. 
This may be tested by placing a straight-edge on them. Those 
that are too high can then be driven down. 

(2) Nail boards against the outside of the stakes, extending 
4 in. over their tops. 

(3) Cross-pieces, of the same diameter as the stakes, are laid 
across the tops and pinned down upon them with wooden pins. 

(4) Nail the side boards to the ends of the cross-pieces, and 
cover the bottom of the boat, which in its inverted position is 
now on top, with boards, and nail the projecting edges of the 
side boards to the bottom securely. 

(5) Finish boarding sides and ends to the proper depth. 

(6) The frame is now ready to be covered with canvas. For a 
boat of the foregoing dimensions, the canvas should be 2SV 2 ft. x 
10% ft., about 6 in. being allowed for lap. The canvas may be put 
together in any number of pieces by daubing the edges of the 
seams with a water-proof composition and connecting them with 
ordinary carpet tacks. 

(7) The canvas having been prepared, it should now be coated 
with a water-proof composition. Tallow, put on hot, will do if 
nothing better can be found. 

(8) Place the canvas on the frame, coated side downward. Tack 
the canvas to the frame and cover with water-proof composition. 

(9) Spike or pin 2 or 3 stout poles to the bottom longitudinally 
(not shown in drawing) to keep the bottom from abrading. If 
these poles are allowed to project about 6 in. at each end. they 
will assist in launching. 

(10) Loosen the stakes from the ground by means of levers. 
Turn the boat over and saw off the stakes about 2 in. below the 
top edge of the side and end boards. 

(11) Pin stout poles to the top of the stakes on the sides and 
ends, and nail the side and end boards securely to them. 

(12) The side poles should project about B in. beyond the ends 
corresponding to those on the bottom, and be lashed to the bot- 
tom poles by means of a rope loop and rack stick. (Not shown in 
drawinsr.) 

(13) Turn the canvas over the top poles and tack ft down. The 
boat Is finished. 

323.— The Box Ponton. Tn localities where planks and boards 



154 Floating Bridges. 

can be conveniently procured, pontons may be constructed very 
expeditiously by placing two partitions of 2 in plank, each 5 ft. 
long and 2% ft. high, in parallel positions, on the top and ends of 
which boards are nailed. (PL 44, Fig. 4.) The box thus formed 
to be covered with pitched canvas, as described in the mode of 
constructing crib pontons. Where sound lumber is at hand, the 
box ponton will be more easily and expeditiously constructed 
than tins crib ponton, but if plank is not at hand it may be prefer- 
able to use poles or split timber rather than wait for it. 

324.— Wagon Body Ponton. Ordinary wagon bodies, cov- 
ered with water-proof canvas or India rubber blankets, may be 
used either as boats or pontons. The small capacity of the 
wagon body requires such pontons to be placed more closely, to 
compensate for it. 

325. — Piers of Barrels. In order to determine the number of 
barrels necessary to form a pier, the buoyancy of a barrel must be 
calculated. This may be done by one of the following rules: — 

(1) Find the contents of the barrel in gallons and multiply this 
by 8 1-3; the result will be almost the total buoyancy in pounds. 

(2) By the formula 

5c I — W = x 
in which c is the circumference of the barrel in feet half way be- 
tween the bung and the extreme end; 1 is the length in feet, ex- 
clusive of projections, measured along a stave, and W is the 
weight of the barrel in pounds; x being the total buoyancy. 
If the barrel is closed, 9-10 of the total buoyancy equals the avail- 
able buoyancy. 

326. — To find the distance between two piers of barrels: Find 
the available buoyiancy of each barrel. Multiply this by the num- 
ber of barrels in the pier. This gives the available buoyancy of the 
pier. To the weight per running foot that the bridge is to bear 
add the weight per running foot of the superstructure. Divide 
the available buoyancy of the pier by this sum; the quotient will 
be the required distance in feet between centers of piers. 

327. — In regard to piers of barrels, the following should be 
noted: 

(1) That piers of barrels, when in bridge, should always be rig- 
idly connected to each other at their ends by tie balks. 



Floating Bridges. 155 

(2) That the tie balks should be lashed to both gunnels of each 
pier. 

(3) That while the roadway balks may not be lashed to the 
gunnels and to each other, it should be done if there is much 
sway to the bridge. 

328. — Piers of Open Barrels. This is the simplest and mosi 
convenient method of using barrels for piers, as it requires only 
a few nails and poles, dispensing with ropes, which are sometimes 
hard to procure. 

To make a raft of this kind, as shown in PL 44, Figs. 5 and 6, 
stand 10 or 12 barrels side by side, touching each other; nail 4 
poles across the outside of the barrels, two at top, two at bottom, 
the nails being driven from the inside into the poles, which, as 
the heads are out, can easily be done. Place another row of bar- 
rels beside the row thus fastened together and nail them to the 
two poles of this row. Nail two poles to the outside of the second 
row of barrels, one at top and one at bottom; push the barrels 
thus connected into the water. 

If too many rows are connected on land they will become too 
heavy to handle. Any number of rows, however, can be attached 
in the manner described above. When the raft is completed, the 
projecting ends of the poles outside are lashed together, and, at 
the points of contact of the barrels, a stout wire nail should be 
driven through and clinched. 

329. — The total buoyancy of a barrel may be calculated by the 
formula given above. If this should be 400 lbs., the safe load for 
smooth water would be at least 300 lbs.; that is, the available 
buoyancy is about % the total buoyancy. A square raft of 10 
such barrels to a side would carry safely 30,000 lbs. 

330. — Piers of Closed Barrels. The usual method of forming 
large barrels into a pier is shown in PI. 43, Figs. 1 and 2. The fol- 
lowing are the successive steps in Its construction:— 

Stores required for a pier of 7 barrels: 7 barrels; 2 gunnels; 12 
slings; 12 braces. 

To build a pier of the foregoing stores, 1 N. C. O. and 10 men 
will be required. The detachment is marched to the site on 
which the material is placed and forms the barrels into piers by the 
following commands and means, 4 men being detailed as gunnel- 
men and 12 as bracemen. 



156 Floating Bridges. 

(1) Align barrels. At this command, the barrels are brought to 
the designated place by the bracemen and aligned, touching each 
other, bung uppermost. 

(2) Place gunnels. At this command, the gunnels are placed 
on the outer ends of the barrels by the gunnelmen. 

(3) Adjust slings. At this command, gunnelmen bring up 
the slings and stand at the ends of the gunnels, the bracemen be- 
ing opposite the intervals between the barrels. The gunnelmen at 
one end place the eyes of the slings over the ends of the gunnels, 
and those at the other end secure the slings to the ends of the 
gunnels by a round turn and two half-hitches. The bracemen 
Keep the slings under the ends of the barrels with their feet. A 
sling is made of 1 in. rope and of sufficient length for an eye splice 
1 ft. long, at one end. 

(4) Fasten braces. At this command, the bracemen, having 
provided themselves with braces, pass the eye of the brace under 
the sling in the center of their interval the end passed through 
the eye and the brace hauled taut, the sling being steadied by 
either foot. The brace is then brought up outside the gunnel, 
directly over the eye, and a turn round the gunnel taken to the 
left of the standing part. 

(5) Haul taut. At this command, each braceman removes 
his foot from the sling and hauls up the standing part of his 
brace with his right hand, holding on to the turn with his left; 
as soon as the brace is taut, the turn is held with the left hand 
and the remainder of the brace in a coil is placed on the barrel to 
the left. 

(6) Cross braces. At this command, each braceman takes the 
brace of the man opposite him from the barrel on his right, pass- 
ing it between the standing part of his brace and the barrel on 
his left, then back between his brace and the barrel on his right, 
keeping the turn below the figure of eight knot on his own brace. 
The end is then placed on the barrel on his right. Each man then 
takes back his own brace from the barrel on his left, passes it un- 
der the gunnel to the left of the standing part, places one foot 
against the gunnel and hauls taut. 

(7) Rock and haul taut. The bracemen, assisted by the gun- 
nelmen, at this command, rock the pier backwards and forwards, 
the bracemen taking in the slack of their braces. 



Floating Bridges. 157 

(8) Steady. At this command, ihe bracemen cease rocking 
and lake a turn round the gunnel to the left of the previous 
turns. 

(9) Secure braces. At this command, the braces are made fast 
by two half -hitches round the two parts of their own braces, close 
to the gunnels, drawing the two parts close together and placing 
the spare ends of the braces between the barrels. 

{10) Turn the pier to the right and adjust sling. At this 
command, the bracemen on the left side, assisted by the gunnel- 
men, turn the pier on its right side. The bracemen on the left 
side adjust the left sling. 

(11) Lower the* pier, turn to the left, and adjust sling. 
At this command, the bracemen on the left, assisted by the 
gunnelmen, lower the pier. The bracemen on the right, assist- 
ed by the gunnelmen, then turn the pier to the left. The 
bracemen on the right then adjust the right sling. The pier is 
complete. 

331. — Should the barrels be very small, they may be put to- 
gether as above described, forming small piers. These can then be 
united in one large pier by cross gunnels. 

332. — Another method of forming barrels into a pier is as fol- 
lows:— (Figs. 3 and 4.) 

Fasten the braces to a balk, two braces for each barrel. Stretch 
out the braces perpendicular to the balk and lay the barrels bung 
uppermost, end to end, on each side of the balk, each barrel over 
its own braces. Upon the cask lay two gunnels, fastened together 
at the ends and one or two intermediate points by lashings, the 
distance between the gunnels being less than a bung diameter of 
a barrel. Secure the braces to the gunnels by two round turns and 
two half-hitches. The lashings connecting the gunnels are then 
racked up. The two end gunnel lashings are lashed to the balk 
beneath the barrels and these lashings are racked up taut. The 
pier is then complete. 

333.— The barrels may be held in a frame, as shown in PL 44, 
Figs. 7 and 8. 

334.— Piers of Logs. In order to determine the number 
of logs necessary to form a pier, the buoyancy of a log must be 
calculated. 



158 Floating Bridges. 

To find the total buoyancy of a log. Multiply the solid con- 
tents of a log by the difference between the weight of a cubic foot 
of the log and a cubic foot of water. 

335.— To find the solid contents of a log. 

(1) Take a mean of the girths or circumference at the ends in 
feet and decimals. Square this mean and multiply it by the dec- 
imal .07956. Multiply this product by the length of the log in 
feet. 

(2) Multiply twice the square of 1-5 of the mean girth by the 
length of the trunk. 

336.— The weight per cubic foot of the timbers usually met 
with will be found in Chap. XV. 

337.— Required the total buoyancy of a pine log whose mean 
girth is 6 ft. and whose length is 35 ft. 

Applying rule 2, we have 

2X|XfX35- 1001 cu. ft. 

lOO* x (02% — 40) = 100 f x 22% = 100.8 x 22.5 = 2,208 lbs. 

As lumber absorbs water, the available buoyancy is taken as 5-0 
the total buoyancy. 

338.— To form a pier of logs. (PL 43, Fig. 5.) The larg- 
est and longest logs should be selected. Branches and knots 
should be trimmed off. The ends of the logs should be painted if 
the, raft is to be used any length of time. The raft should be 
built in the water. Select a place where there is little current 
and where the bank slopes gently to the stream. Throw the tim- 
ber into the water and moor it close to the shore. Note the nat- 
ural position of each log in the water before putting it in the rait. 
The up-stream end of each log should be drawn on shore and bev- 
eled to a whistle shape, so as to present less obstruction to the 
action of the current. 

Arrange the timber in the position it is to have in the raft, the 
butts alternately up and down stream, the up-stream ends forming 
a right angle, salient up stream. The first log is brought along- 
side the shore and the end of a plank or a small trunk of a tree 
fastened with trenails or spikes to it about 3 ft. from each end. 
The log is then pushed off a little, a second log brought up under 
the transoms and in close contact with the first. The second log 
is then spiked like the first, and so on for each remaining log. 
Care must be taken to place the whistle ends up stream with the 



PLATE 45. 




PLATE 46. 




PLATE 4?. 




PLATE 48 




Floating Bridges. 163 

bevel underneath, and to spike the transoms perpendicular to the 
logs. If the stream is very gentle, the up-stream ends of the logs 
need not be placed as in' Fig. 5, but may be parallel to the 
transoms. 

Another method is to lash the logs together and fasten on the 
transoms with spikes or trenails. Or, lash the logs together and 
lash the transoms to the logs, tightening the lashings with rack 
sticks. 

339.— Two additional transoms should be placed on the raft 
by whatever method employed in putting on the first. They 
should be the distance of the roadway or platform apart, at equal 
distances from the center of gravity of the raft, and bear upon all 
the logs. In order to obtain sufficient buoyancy, and allow suf- 
ficient water way, several courses of timber may have to be em- 
ployed. For use in a bridge, a raft should have an available 
buoyancy of. 15,000 lbs. 

340.— If the raft is to be used as a flying bridge, it should have 
the shape of a lozenge. (PL 43, Fig. 8.) 

341.— Anchors. Anchors for the U. S. Advance Guard Bridge 
Train weigh 75 lbs., and for the Reserve Train 150 lbs. These 
will be sufficient for moderate streams. An anchor with the 
names of the various parts is shown in PL 45, Fig. 1. 

342.— The distance of the anchor from the bridge should be 
at least 10 times the depth of the stream; otherwise the bow of 
the boat or ponton will sink too deep in the water. The direction 
of the cable must be the same as the current The anchor cable 
should be of 1 in. rope and attached to the anchor ring by a fish- 
erman's bend. A buoy might be attached to the anchor by means 
of a %-in. breast line, in order to mark its position and serve as 
a means of raising it. The breast line is attached to the buoy 
ring by a fisherman's bend and round the shank of the anchor, 
close to the crown, by a clove hitch. 

343.— The number of anchors will depend on the strength of 
the current. It is generally sufficient to cast an anchor up-stream 
for every alternate boat or ponton, and half that number down- 
stream. If the stream is rapid, every boat should be anchored 
up-stream. 

If very rapid, the bridge must be secured to a hawser, as shown 
in PL 46, Fig, 1. If the bridge is short, ropes can be stretched 



164 Floating Bridges. 

from the piers to the banks. (Fig. 2.) If anchors are scarce, one 
may be attached to two piers. (Fig. 3.) 

Before being cast, the anchor should be well stocked. Rafts 
of casks or timbers bring a greater strain on anchors than boats 
or pontons. 

344.— Substitutes for Anchors. One or two spare wheels 
with tires and felloes removed. (PL 45, Figs. 3 and 4.) Two or 
more pick-axes, laid together or fixed on one handle. (PL 46, Fig. 
4.) A harrow with lengthened teeth, loaded with stones. Ga- 
bions filled with stones. Large stones or railway irons. Nets 
filled with stones. Frame filled with stones. (PL 45, Fig. 2.) 

Care must be taken to allow the anchor to fall in good holding 
ground. For this purpose, a direction oblique to the current may 
sometimes be allowed. 

345.— Forming Floating Bridges. Floating bridges may 
be formed in the following ways: — 

(1) By successive pontons or boats. 

(2) By parts. » 

(3) By rafts. 

(4) By conversion. 

346.— By Successive Pontons. (PL 49.) This may be done 
in two ways: — 

(1) By adding to the head of the bridge, the tail being station- 
ary. This method requires the roadway material to be carried an 
increasing distance. The men, however, do not have to work in 
the water. 

(2) By adding to the tail of the bridge, the head, already con- 
structed, being constantly pushed into the stream. The materials 
do not have to be carried so far as in the first case, but it requires 
a number of men to work in the water and is not advantageous 
where the bank is steep. 

In the first method, those boats or pontons which cast up- 
stream anchors should be moored above the approach to the 
bridge, the others Below. 

347.— By Parts. (PL 49.) In this method, the boats or pon- 
tons are brought close to the shore above the bridge. For con- 
venience in putting the parts together several chess are laid from 
the bank to the interior gunwale of one boat or ponton. The 
boats or pontons forming the part are then brought in place and 



PLATE 49, 




166 Floating Bridges. 

balks placed on them. The chess forming the roadway are then 
placed on the balks, excepting a sufficient number at each end of 
the part to allow for the insertion of a bay between the parts. 
The parts, all constructed as directed, are then placed in position, 
each part carrying enough material to construct the connecting 
bay. The parts are joined with each other and with the abut- 
ment bay, which has been previously constructed. 

348.— By Rafts. Each raft formed of 2 or more piers is con- 
structed complete and the rafts come into the bridge in succes- 
sion. Each of the methods, bridge by raft and bridge by parts, 
has the advantage of simultaneously employing a large number 
of men. (PI. 49.) 

349.— By Conversion. (PI. 49.) In this method, the bridge 
is put together entire along the shore above the selected site. A 
tributary stream may be advantageous for this purpose. The 
bridge is then floated toward the site, care being taken to prevent 
the pivot end from touching the shore and the wheeling end from 
turning too fast. 

350.— The various methods above described may be combined 
in the construction of one bridge. 

The connection of the bridge with the shore may be made by 
allowing the balks to rest on an abutment sill let about 1 ft. into 
the ground, or by a trestle. 

' 351.— If the stream is to remain open to traffic, it is well to 
hav« two or more rafts in mid-stream, arranged to swing so as to 
allow boats to pass, or the halves of the bridge may be swung for 
this purpose. Usually the passage is made by allowing the rafts 
or halves to swing with the current; they are then brought back 
against the current. 

352. — Floating Objects. Some arrangement should be made 
to protect the bridge from floating objects. This mav be done:— 

(1) By a guard of observation, stationed above the bridge, pro- 
vided with boats containing anchors, grapnels, hammers, chains, 
etc. The object may be turned ashore, or, if this is not possible, 
an anchor may be attached to it to break its momentum. 

(2) By a floating stockade, constructed of trees united by 
chains and forming a continuous barrier to floating objects. Its 
direction should be about 20° with the current. 

(3) By constructing the bridge by rafts and withdrawing the 
menaced part, thus allowing the object to float past. 



Floating Bridges. 



167 



352a. — Improvised Floating Bridge.* A practical improvised 
floating bridge having a wagon-road 10 ft. wide was constructed 
at Molo, Island of Panay, P. I., across a tidal stream 300 ft. wide, 
and is described as follows: 

Floating piers at intervals of 10 ft, consisting of bundles of 
25 bamboo poles ("a"), supported the roadway, which consisted 
of a mat of interwoven bamboo strips ("b") resting on a bamboo 
corduroy ("c"), which in turn rested on four hard wood balks, 
2y 2 in. x 4 in. in cross-section ("d"). Rattan lashings were used 
throughout and aprons were improvised at the shore ends of the 
bridge to allow for the 3-ft. rise and fall of the tide. 




In anchoring, advantage was taken of the piles, of a former 
bridge, as shown in sketch. The bamboo crib ("e"), built loosely 
around the pile, rose and fell with the tide and prevented the 
bridge from floating either up or down stream. The buoyancy of 
this bridge was such that infantry in column of fours did not 
bring the balks into the water. 



♦This bridge was constructed, using native labor, by Captain B. F. Cheatham, Q. 
M. U. S. Army, in June, 1899, and was still in use a year later. 



CHAPTER XVII.— Roads. 

353.— The frequent necessity, in the field, for the construction 
of a short piece of road, or the repairing of existing roads, makes 
it important that all who may at any time have this work in 
charge should be familiar with the principal requirements of it. 

354. — Two desirable conditions in a road are that it be straight 
and level; where both cannot be obtained, straightness is sacri- 
ficed to levelness. Other things being equal, the length of a road 
may often be advantageously increased 20 ft. for every foot of 
vertical height avoided. 

355.— Limiting Gradient. As levelness cannot always be ob- 
tained, various considerations fix limits for the steepness, called 
limiting gradients, which are to be used only when unavoidable; 
thus, for a very short distance, as an approach to a bridge, the lim- 
iting gradient may be 1-10; a grade of 1-12 should not exceed 100 
ft.; one of 1-15 should not exceed 200 ft.; 1-20 should ordinarily be 
the limiting gradient for easy travel, while 1-30 to 1-35 is still 
better. 

356.— Compared to what he can draw on a level, a horse can 
draw only about 90 per cent on a grade of 1-100, 80 per cent on 
1-50, 50 per cent on 1-24, and 25 per cent on 1-10, but for a short 
distance he can exert 6 times his ordinary force. 

357.— A road should, if possible, always rise continuously to 
its highest point and nowhere descend partially again. 

358.— "Width. For military purposes roads should be wide 
enough to allow wagons going in opposite directions to pass each 
other easily; this is usually taken at 16 ft. For wagons going in 
one direction only or with turnouts at intervals, and for infant- 
ry in column of fours, or cavalry in column of twos, 9 ft. will suf- 
fice, and for pack animals 6 ft. At turns in a zig-zag road up a 
hill the road should be level and the width increased from y± to %. 

359.— Form. The best for the upper surface is that of two 
planes inclined at an angle of about 1-24 and joined by a slight 
curve 5 ft. long. (PL 50, Figs. 1, 2 and 13.) 

Between the road and ditches should be flat mounds raised 6 
in. or more above the surface, with sloping sides covered with 
sods or stone next to road, forming with roadway the gutters: 



PLATE 50. 




Covered 
JDrains ' 



^Water Table 

FIG. 15. 



/f^ 




Wt- 



170 Roads. 

they serve also to hold up the road material and as warnings at 
night of the proximity of the ditch. 

On the hillside the surface should be a single plane inclined 
towards the hill. (Figs. 3, 4, 5, 7 and 8.) 

360.— Road-bed. The surface of the road-bed should be dug 
out or built up and solidly compacted, either by rolling or ram- 
ming, and when ready to receive the road material should be of 
the same shape as the surface of the finished road, with shoulders 
at the sides to retain the material in place. (Fig. 13.) 

On hillsides of gentle slope, the road-bed is usually made of 
half cutting and half filling, the lower side of the slope being 
stepped to retain the earth excavated (Fig. 3); on steep slopes it 
is often necessary to both step the slope and build a retaining 
wall of stone (Fig. 4), or of logs (Fig. 5), or of other materials; on 
very steep slopes it may be necessary to build retaining walls on 
both sides (Fig. 7); while in rocky formations the excavated hill- 
side may be left nearly vertical. (Fig. 8.) 

361.— Drainage. Nothing is of greater importance in road- 
building than proper drainage. It is the life of a road. In a 
level country it is necessary to raise the road-bed to keep it 
always free from water. None must be allowed to remain on the 
surface and all must be drained from beneath. To accomplish 
thjs ditches must be dug on both sides of a road on level ground 
and in cuttings, from 2 to 3 ft. below the road-bed and of a width 
depending on the amount of water to be discharged. (Figs. 1 
and 2.) In wet places, low-lying lands, clayey and springy soils, 
the ditches must be deeper and sub-drains 3 to 5 ft. below the 
road, emptying at intervals into the side ditches, must be made to 
keep it dry. (Fig. 1.) 

Rain falling on the surface of the road is collected in the gut- 
ters on the sides and run into the side ditches by drains at fre- 
quent intervals. 

On a hillside, between the road and the hill is the ditch, from 
which the water is discharged through culverts or covered drains 
under the road into the natural watercourses. Catch drains 
along the top of the cutting are made to prevent the slopes being 
washed down and the water from above finding its way to the 
road. 






Roads. 171 

Wliere open ditclies are liable to become filled, some kind of 
covered drain must be used. (Figs. 5, 10, 11 and 12.) 

Theoretically, a road should be perfectly level, but for pur- 
poses of drainage, in the direction of its length, it should have at 
least a slope of 1-125. 

On a steep road, shallow paved water tables extending oblique- 
ly across the road are sometimes necessary to catch the water 
running down the road and carry it to the gutters, or small 
mounds crossing the road obliquely are substituted. (Fig. 9.) 

362. — The surface of a road ought to be as smooth and as hard 
as possible, for which purpose various kinds of covering material 
are put on the bed. 

As the road-bed must be kept thoroughly dry at all times by 
the ditches intercepting all ground water, so the stone or other 
covering must be so thoroughly rolled and compacted that no 
water falling upon the surface can possibly find its way down to 
the foundation and through it to the bed. 

363.— When roads are made of broken stone the material in 
the Telford class is composed of two parts: the foundation and 
the covering. (Fig. 1, right half.) The foundation consists of 
a uniform thickness of not less than 5 in. of any durable broken 
stone with bases about 5 in. x 10 in. laid close together by hand, 
larger faces down, firmly wedged with smaller stones in the in- 
terstices, and the whole sledged and rolled to a uniform sur- 
face. Then a thin layer of binding material, as clay or loam, is 
sprinkled over it and rolled. On this is put the covering, consist- 
ing of a layer of about 3 in. of broken stone of uniform, well- 
shaped cubical pieces which will pass through a ring from 2 to 
2% in. in diameter, and rolled to a uniform, compact surface. 
Then another layer of binding material is added and well rolled. 
Another layer of stones, 3 in. thick, of sizes from 1 to 2 in. in diam- 
eter, is next spread and rolled as before. On this may be spread 
another binding coat, well rolled, then a thin layer of fine screen- 
ings or fine gravel free from dirt. Often, where traffic is light 
and expense large, a single layer of broken stone 4 in. thick is put 
on the foundation. 

364.— In the Macadam class (Fig. 1, left half) the hand-laid 
foundation is not used, but generally three layers, each from 3 to 



172 Roads. 

4 in. thick, of broken stone and binding coats, as described above, 
are spread and rolled until smooth and compact. 

For light traffic a single layer of 4 in. is sometimes used. 

365.— The best stone is a compact, fine-grained syenite, basalt 
or trap rock. Hornblend, actinolyte, dioryte, and some other 
rocks make good material. Quartz and flint, though very hard, 
are brittle, difficult to work, and not so good. Granite, on ac- 
count of mica in it, breaks up and grinds away too easily. Gneiss 
is poorer than granite. Slatey rocks generally break up too eas- 
ily. Limestone, generally too soft, grinds away easily, making a 
very disagreeable dust. Softer stones may be used for the foun- 
dations and lower layers, but only the hardest and toughesl 
should be used for the coverings. 

366.— Earth roads require even greater care in draining, grad- 
ing, and forming the surface than those described, and a trans- 
verse slope, not less than 1-20, to hasten the flow of surface water 
to the gutters. No sods or vegetable refuse should be allowed in 
grading or filling ruts, only gravelly earth, if obtainable. 

Roads are frequently made with a metal portion in the center 
and earth roads, called wings, on the sides. (Fig. 2.) 

367.— It is almost impossible to construct a road of clay which 
will be good in wet weather, but a very sandy road may be im- 
proved by working a little clay in it. 

368.— For gravel roads the bed is first formed as described. 
The gravel is screened to remove stones larger than 2V 2 in. in 
diameter and such as are less than % in.; and all earthy matter. 
A layer of the screened gravel, 4 or 5 in. thick, is then spread anH 
rolled, then another layer of 3 or 4 in., which should also be well 
rolled. 

369.— Repairs. Ruts appearing should be immediately filled 
in, and traffic directed over all parts of road Before spreading 
stones, all mud should be cleaned off and the surface picked up a 
little to allow the new stone to bind into the old, wet weather be- 
ing preferred, or the stones should be sprinkled. Ditches and 
culverts must be cleaned as needed. 

370.— Tn crossing marshy ground that cannot be well drained, 
corduroy roads made of logs of suitable lengths laid side by side 
across the road, over which is spread a covering of earth or gravel, 
are sometimes used. 



Roads. 173 

371.— Brushwood, made into fascines and hurdles, may be 
used the same way as a foundation. With fascines, the top row 
should extend across the road and be of a length equal to the 
width of road. (Fig. 6.) 

372.— Where lumber is the cheapest material, plank roads may 
be built by first laying parallel rows of sleepers or sills flush 
with the ground, about 4 ft. apart, in the direction of the road, on 
which boards, 3 in. thick by 9 to 12 in. wide and 8 ft. long, are 
placed crosswise. 

373.— The construction of communications to all parts of a 
position to facilitate the movement of troops, etc., from one part 
to another, is almost always a certain necessity. These would 
rarely be more than temporary, but, if made on the lines indi- 
cated, as far as time and requirements permitted, so much the 
better. 

374.— Roads and paths may have to be cleared through woods; 
wet places made passable by corduroying or filling up with brush, 
fascines, etc.; and approaches made to ascend steep places. 

Wherever roads cross or separate, signs should be put up tell- 
ing exactly where each leads. 



PLATE 51 



FIG.l. 



FIG.2. 



I 



Pt-ATt 



d a a a o o 



T 



■J-n-4- 



1 



t /sh PlAmss 




FIG 3. /fartfrrd Itessed Steel jRe. • EIG5: 

4 



9 2. 




Crossing 

FIG.12. 



CHAPTER XVIII.-Railroads. 

375.— Id military operations, the principal duties of troops in 
connection with railroads will be either tiie repairing of lines that 
have been partially destroyed, or the destruction of lines to pre- 
vent their use by the enemy. 

376.— A railroad, as existing in its completed form, will be 
briefly described to indicate the state to which it should be 
brought by repairs after destruction, and to so familiarize one 
with it as to suggest methods of most effectually destroying it. 

377.— A railway line consists of a series of straight lines of 
different lengths, called tangents, which are joined by curves. 
The road-bed is first prepared with a smooth hard surface (slop- 
ing slightly from the middle to each side for drainage) from 10 to 
12 ft. wide for a single track, and from 21 to 25 ft. for a double 
track. On this is placed the ballast, from 12 to 24 in. thick, of 
broken stone, gravel or cinders, etc., for the purpose of distribut- 
ing the load over a larger surface, holding the ties in place, carry- 
ing off the rainwater, affording a means of keeping the ties up to 
grade line and giving elasticity to the road-bed. 

378.— The ties are generally of wood, hewn flat on top and 
bottom, from 7.5 to 9 ft. long, 6 to 10 in. wide, and about 7 in. 
deep. It is customary to sink them about half their depth into 
the ballast. Their object is to hold the rails in place and furnish 
an elastic medium between the rails and ground. The distance 
apart is usually 2.5 ft. from center to center, but depends upon 
weight of engines and strength of rails. They should be uni- 
formly spaced to distribute the weight equally. 

Tie plates (PL 51, Figs. 3 and 7) are often used to prevent the 
rails from crushing into the ties. 

379.— Tests of metal ties in the interests of economy and effi- 
ciency have been made with satisfactory results. On some level 
portions of the N. Y. Central R. R. are used the Hartford pressed 
steel tie (Figs. 1 and 2), to which the rails are fastened by clamps 
bolted to the tie. 

380.— The form of rail used in the United States is shown in 
Fig. 3, being the "T" rail, which varies in weight from 12 to 100 
lbs. per yard. The mean dimensions of 80 lb. rails are given on 
<-12- 



176 Railroads. 

left-hand side of figure and of 100 lb. rails on right-hand side. 
They are placed 3 ft. apart for narrow gauge, 4 ft. 8.5 in. for 
standard gauge, while ft. is the broadest gauge in the United 
States, measured from inside to inside of head. The tops of rails 
must be slightly inclined to fit the cones of the wheels. 

381. — The weak part of a track is at the joints. The old 
method of using chairs under the ends of rails has about ceased, 
the practice now being to fish the joints by plates (Fig. 1), and 
angle irons. (Fig. 3.) There are also used what are known as 
the Reinforced rail joints (Fig. 4), Bridge rail joints (Fig. 8), Dou- 
ble Girder rail joints. (Fig. 9.) 

382.— Rails are fastened to the ties by spikes, the best being 
made with sharp, chisel-edge points, clean, sharp edges, and 
smooth surfaces, so as to cut and press aside the fibers of the 
wood, instead of tearing them. Attempts to increase the hold- 
ing power by jagged or twisted spikes have been unsuccessful. 
On bridges, interlocking bolts (Fig. 6) are much used instead of 
spikes. To keep the track in the right line, allowance must be 
made for the contraction and expansion of the rails, by not plac- 
ing them in contact at the joints, and the holes for the bolts must 
be elongated. 

383.— The centrifugal force of a train passing around a curve 
tends to throw the wheels against the outer rails, which is par- 
tially counteracted by raising them to throw the center of gravity 
inward and cause the car to slide inward. Each rail in a curve 
ought to be bent to fit the curve before being laid. 

384.— On single tracks, there are laid at occasional intervals 
short pieces of track, called sidings, to enable trains to pass one 
another. The arrangement for passing from one track to another 
is the switch, which consists of a single length of rails, movable at 
one end by a lever, so as to connect with either pair of rails. The 
simplest form is the stub switch (Fig. 10), which leaves one line 
always open while the other is continuous. The one in common 
use is the split or point switch. (Fig. 11.) Various devices are 
used for locking and interlocking switches, to avoid accidents. 
At the points where the inner rails cross is placed a frog (PL 52, 
Fig. 1), which enables the wheels to pass over the inner rail of 
the other track. 



PLATE 52. 



FIG 1 




FK-8. 



c/1 



178 Bail roads. 

385.— Crossings occur where two tracks intersect, and consist 
of four frogs and corresponding guard rails. (PI. 51, Fig. 12.) 

386.— Where one main line passes to another is called a junc- 
tion and the ordinary switch is used. In crossing from one track 
to a parallel track the rails are arranged as in PL 52, Fig. 2. 

387.— A wye, from a similarity to the letter "Y," is an arrange- 
ment of tracks for turning around engines and cars and connect- 
ing cross-roads. (Fig. 3.) 

388.— Turntables are platforms, turning on rollers upon an 
underground circular track, used to transfer engines and cars 
from one track to another and to turn them around. 

389.— The locomotive engine is the power on railroads. They 
weigh up to 232,000 libs, without tender, and to 292,000 lbs. for 
passenger to 365,000 lbs. for freight, with tender, and draw 2,400 
or more tons on a level. The amount of coal consumed being from 
40 lbs. to 70 lbs. per mile run. 

390. — The rolling stock consists of passenger cars for about 60 
persons, 48 to 52 ft. long, 9.5 ft. wide, weighing from 40,000 lbs. 
to 60,000 lbs.; sleeping cars for 64 passengers, 60 to 70 ft. long, 
9.8 ft. wide, weighing 60,000 lbs. to 90,000 lbs.; mail, express and 
baggage cars, 45 ft. long, 9.3 ft. wide, weighing about 27,000 lbs.; 
freight cars consist of Box, Refrigerator, Hay, Furniture, Oil, 
Stock, etc., and are about 34 ft. long, 8.5 ft. wide, weighing from 
20,000 lbs. to 30,000 lbs., capacity 20 to 30 tons; flat cars, 34 ft. long, 
weighing 16,000 lbs. to 19,000 lbs. Height of top of box cars above 
rails about 15 ft. Freight cars are being rapidly provided with the 
M. C. B. automatic couplers. (Fig. 4.) 

391.— The buildings consist of passenger and freight depots, 
engine houses, fuel sheds, water tanks, repair shops, and section 
houses. At convenient points are generally located yards where 
stock can be loaded and unloaded. It may sometimes be neces- 
sary, however, to load and unload animals and supplies in the 
field along a railroad where there are no platforms or other con- 
veniences, which must then be built. 

392.— A simple form of ramp, in the absence of anything 
better, could be made by taking 3 or 4 planks 3 in. thick, 10 to 12 
in. wide, and 10 to 14 ft. long, fastening them together side by 
side, preferably by footholds nailed across on top and several 
cleats on the bottom; otherwise, by lashing, wiring or by stakes 



Railroads. 179 

at the bottom when in position, and wedges in the car door. The 
ends on the ground should be slightly sunken and rested against 
a cross beam. Ropes should be hung along the sides and blankets 
or canvas hung on them. Frops of some kind, as sacks of grain, 
bales of hay, etc., can be placed under the middle to strengthen 
it if necessary. 

393. — Another form of portable ramp, which could be carried 
on all railroad trains where they might be needed, consists of 6 
long timbers 4 in. x 4 in. x 14 ft., 6 short timbers 4 in. x 4 in. x 6 
ft., 24 boards 1.5 in. x 12 in. x 6 ft. with footholds nailed length- 
wise on one side. 

To load or unload horses, rest the ends of three or four of the 
long timbers, equally spaced, on the car floor, the other ends resting 
against a short timber, sunk in the ground and staked down. On 
these place the boards forming the floor; on each side of the ramp, 
on the boards, lay a long timber and fasten the ends to the timbers 
underneath. The boards should have cleats on under side to 
prevent slipping sideways. If necessary, some of the remaining 
boards can be set edgewise between posts of the short timbers 
as an intermediate support. 

394. — To unload a number of cars, enough men can be placed un- 
der the ramp, near the car, to raise it high enough to allow the car 
to be removed and another run in place, thus avoiding taking 
the ramp apart for each car. 

395.— Semi-permanent platforms and ramps may be made as in 
Figs. 6 and 7, if rails and boards are available. 

396.— To load or unload wagons and guns from a flat car, place 
the ramp against one end (Fig. 8^, using four long timbers for 
stringers on which the boards are placed, the other two long tim- 
bers being used for side rails. Support underneath with boards 
set on edge, held between some short timbers, or with bales of 
hay, sacks of grain or otherwise, as necessary. A couple of 
boards can be used to run the wheels from the car on to the ramp 
nnd others at the foot of ramp to carry the wheels across the rails. 
The lower ends of the stringers should abut against a tie, if pos- 
sible: if not, they should be staked down. 

397.— PI. 53 is a design of a portable ramp devised by Major 
E. G. Fechet, Oth U. S. Cavalry. The ramp consists of 7 boards 
1,5 in, x 7 in. x 12 ft., joined together in three sections (2 for the 



PLATE 53. 




Railroads. 181 

outside, "A," "A"; and 3 for the middle one, "B"); by wooden 
strips "C," 1 in. thick, and 2 in. wide, bolted to the upper surfaces, 
1 ft. between centers; these strips also serve as footholds. Along 
the middle of the outside boards extends a side rail, "D," 3 in. x 
3 in., held firmly by the iron straps, "E," % in. x 2 in. On the out- 
side of each side rail are 3 sockets "F," for standards "G" 3 ft. 
high, along the tops of which are to be stretched ropes or chains 
from which canvas or blankets are hung. On the under side of 
each section 3 ft. apart are bolted iron cleats, "H," 0.5 in. x 2 in., 
beginning at 18 in. from the ends. On the ends of each section are 
bolted iron claws, "K," for catching the car floor or door slide, to 
prevent slipping when in position for use. The three sections are 
held together for use by 4 iron tie bars, "L," 0.5 in. x 2 in., which 
are placed under the cleats "H," and the whole firmly keyed as 
shown. This form of ramp may be made longer or shorter, nar- 
rower or broader, as desired. By taking out the standards it may 
be hung on the side of a car between a door and end. It is easily 
taken apart and transported in a wagon, and as easily put to- 
gether when needed. It is designed to combine both strength 
and lightness. It weighs about 400 lbs. complete. 

398.— Disabling" and destroying railroads. Under the head 
of disabling will be mentioned means, the effects of which will 
only temporarily interrupt traffic, leaving the road repairable af- 
ter some delay. 

399.— Under destroying, such as are more serious in their 
effects; either causing extensive repairs or a change of route to 
avoid them. 

400.— The disabling of railroads will usually be done by raid- 
ing parties of cavalry, while the destroying of them may be done 
by such parties or by specially detailed troops trained for such 
service. 

401.— It must be understood that no railroad is to be destroyed 
except upon the orders of the officer commanding in the field. 
If otherwise, and it should be taken from the enemy, the dam- 
age done might seriously embarrass future operations. Before 
ordering any destruction the questions will arise — "Is destruction 
absolutely necessary?' "Will it be of no further use and is every 
hope of regaining it gone?" "Are the advantages to be gained 
sufficient to compensate for the damage that will be done?" All 



182 Railroads. 

the attending circumstances should be carefully considered, es- 
pecially if in one's own country. The choice of points for de- 
struction and the most effective means are subjects for study. It 
is useless to destroy anything that will not seriously embarrass 
traffic. 

402.— A railroad may be disabled by removing rails at vari- 
ous intervals, then destroying or hiding them; or, if a large num- 
ber of men are at hand, select a high embankment, line the men 
along on one side of the track, disconnect the rails at each end of 
the line of men, then, at a signal, they raise the track on edge and 
let rails and ties together go over the embankment. Thus treated, 
rails and ties must be separated before being replaced. An im- 
provised wrench for removing nuts on fish-plates is a bolt with 
two nuts on it, just far enough apart to grasp the nut to be re- 
moved. (PI. 52, Fig. 5.) If time is an object, remove outside 
rails on a curve, or disconnect a joint on each side and throw them 
as a switch to derail the train either on an embankment or in a 
cut, or use explosives as described in Chap. XX. 

By laying rails across a pile of burning ties until red hot in the 
middle they may be easily bent around a tree or telegraph pole; 
they may be twisted by heating, as above, then using bars or pick- 
axes placed in the holes in each end and working in opposite 
directions. 

They may be torn from the ties and twisted cold by using Gen. 
Haupt's "U"-shaped rail-twister, shown on PL 40, Fig. 8. Ten 
men with two twisters, two axes, two stout pieces of rope 35 ft. 
long, can tear up and twist a rail in 5 minutes. The junctions of 
lines are important points to attack to disable a track. 

Water tanks may be rendered useless for a time by breaking 
holes in them, removing pistons from pumps, etc. Fuel, ties, and 
small bridges may be burned. Engines may be disabled by burn- 
ing out the flues, removing or breaking different parts of the ma- 
chinery, filling suction pipes of pumps with waste, or by removing 
bolts from eccentric straps, etc. Cars may be disabled by removing 
couplers, axle boxes, breaking or removing trucks, etc. The use 
of mines under the tracks, so arranged as to be exploded by the 
passing of trains, is inn effective method of interrupting traffic and 
shaking the morale of troops being transported. 

403.— To destroy a railroad, if time is sufficient, remove roll- 



Railroads. 1 83 

ing stock, rails, etc., to the rear. Otherwise, destroy large bridges, 
if of wood, by burning, using oil if it can be obtained, or by ex- 
plosives, as in Chapter XX.; if of iron, steel, or masonry, by ex- 
plosives, as in Chapter XX. If there are tunnels ou the line, 
select longest ones and blow them in at as many points as possi- 
ble, or cause two wild trains to collide in the middle, afterwards 
blowing in the ends. Those with sandy soil are the best. Deep 
cuttings with retaining walls may be filled in by use of explo- 
sives. If trees, poles, wires, etc., can be mixed in— so much the 
better. Blow up tanks and engines, burn aU fuel, cars, repair 
supplies, etc. Fire a cannon ball through engines. 

404.— The repair of railroads will best be accomplished by 
a construction corps having some of the elements of permanency 
in its organization; or, at least, by small squads of experienced 
men, to which others could be added by temporary detail, when- 
ever active operations require such increase. They should be 
established as near to where their services may be needed as 
possible. 

405.— Bridges should, in the beginning, be classified and num- 
bered, so that a single reference to the class and number will give 
complete information as to its character, dimensions, etc. At 
designated points will be kept on hand, already prepared for put- 
ting in bridge, suitable materials for the repair of each class. 
This was done by the Union Army from 1861 to 1865, so that, 
when word was received that a certain bridge had been destroyed, 
by a reference to the class and number the reconstruction corps 
started out carrying with it just what was needed to repair the 
bridge. Even complete trusses for the larger class of bridges 
were prepared and kept ready for use. 

406.— Tunnels and cuts which have been filled up can gener- 
ally be cleared only' from the two ends. 

407.— Rails, fish-plates, spikes, ties, etc., will be kept in store 
at secure places, for repairing any portions of destroyed track. 
Rails which have been simply bent can be straightened by various 
means. Gen. Haupt's method was as follows: Two ties were 
placed on the ground, across these two more ties and on top n 
single tie, which was cut across one-half the depth of the rail 
to receive it and prevent it turning. Weight was applied at the 
two ends of the rail by men bearing down on poles placed there- 



184 Railroads. 

on. The rail being moved back and forth until straightened, re- 
quiring from 4 to 5 minutes. Rails which had been heated and 
bent to a very sharp angle required more time, necessitating re- 
heating and hammering until straightened. For this purpose, at 
special points, were prepared furnaces consisting of two parallel 
walls of brick, stone or clay, with a kind of grate. The straight- 
ening table consisted of a large, square timber as long as a rail, 
on which were securely fastened three rails, as in PL 52, Fig. 9, 
^n which the lieated rail was laid and hammered until straight- 
ened. Twisted rails require rerolling before they can be again 
used. 



PLATE 54. 




CHAPTER XIX. -Telegraph and Telephone Lines. 

408.— In order that telegraphic messages may be sent from 
one point to another, it is necessary that there be a continuous 
metallic conductor from the first to the second point, and that 
this conductor be insulated from contact with the ground or with 
anything leading to the ground. The conductor used in construct- 
ing permanent lines is of galvanized iron wire, generally of size 
No. 9. In military lines it is generally somewhat smaller on ac- 
count of the weight, and sometimes of bare copper wire about No. 
14. The wire is carried on poles and tied to glass or other insu- 
lators which are attached to the poles. 

409.— Poles should be not less than 22 feet in length nor less 
than 7 and 5 inches in diameter at the larger and smaller ends 
respectively, but may be as much longer and larger as de- 
sired, and should be stripped of bark and pointed at the 
upper end. The holes for poles should be not less than 1-6 the 
length of the pole in depth. The poles should be raised as shown 
in PL 54, Fig. 1, and held vertically while the excavated earth is 
thoroughly tamped in from bottom to top; after the hole is com- 
pletely filled, the earth should be made into a small mound so as 
to shed water. 

410.— When the brackets are attached to the pole directly, a 
seat should be cut in the pole with a hatchet and the bracket 
should be nailed on, using 1 twenty-penny and 1 forty-penny 
nail. Where the poles are intended to carry several wires, cross- 
arms are bolted to the poles, fitting into seats cut for them. The 
arms carry brackets not less than 15 in. apart. The arms should 
not be less than 20 in. from one another. Not less than 25 poles 
to the mile should be used, and usually the number is increased 
to 30. 

411.— Every 5th pole should be protected from lightning dis- 
charges by having a piece of line wire run from about 6 in. above 
the top of the pole to the ground. This wire must be so arranged 
that it cannot come in contact with the line wire should that 
become unfastened. Poles should be vertical except when nec- 
essary to incline them to resist strains when thev will be set 
at a slight inclination in such manner that the comnonent of 
the strain in the direction of the length of pole will tend to 
press it into the ground. Where exposed to great strains, or 



Telegraph and Telephone Lines. 187 

to continuously high winds, it may be necessary to guy the 
poles: this is done with stays consisting of two or more line 
, wires twisted together and fastened near the top of the pole, the 
ground end being attached to a section of a pole or timber suita- 
bly anchored in the ground, as shown in Fig. 2. Where possi- 
ble, the line of poles should be run on one side of the road and 
< far enough from it to be safe from accidental damage by pass- 
ing wagons. Where roads have to be crossed, the wire should 
be carried over on high poles so as to clear any possible wagon- 
load. 

412.— The insulators in common use in this country are of 
j glass and of the form shown in Fig. 3. The one shown in Fig. 4 
I is preferable, as it is not so liable to cause leaks on account of 
, moisture accumulating and forming a connecting film to the 
j bracket and from that to the pole. 

413.— The wire is attached to the insulators by pieces of wire 

I called ties. These are generally of the same wire as the line. 

, They are annealed and formed on an insulator and cut long 

i enough to embrace the insulator and project 3 or 4 inches beyond 

the line wire. 

414.— To hang the wire. The wire is carried up to the top 
of the pole and the lineman places a tie on the insulator, the line 
wire against the insulator above the tie wire, and bends the 
ends of the tie wire upward so as to sustain the line wire. The 
line wire is then strained by the lineman, either by means of 
hand power or by use of the wagon carrying the reel. When 
the line wire is stretched so that it sags but about V/ 2 ft. in 70 
yds., the tie wire is wrapped around it about one and a half 
times, finishing with the ends of the tie wire pointing towards 
the insulator; this secures the line and completes the work. 
(Fig. 5.) 

415.— In open country the line wire is strung on the insulator 
on the side towards the pole, so that, if it becomes accidentally 
undone, the wire will not drop. If in timbered country, then 
hang it on the side from the pole, so that when trees, etc., fall 
against the wire it will simply tear it away from the insulator, 
but will not break the line wire. When necessary to hang the 
wire on trees, a regular tree insulator should be used, and in 
default of this, the tie shown in Fig. G may be used, the ends 



188 Telegraph and Telephone Lines. 

being wound loosely so as to allow of an easy lateral motion to 
accommodate the swing of the tree. The poles should be num- 
bered at each mile so as to aid linemen to report location of breaks 
and repairs. 

Streams are crossed by hanging the wires on strong, high sup- 
ports, taking care not to strain the wire so much as to cause it 
to break. 

416.— The description of instruments and batteries, their con- 
nections and care, will be found in the Manual published by the 
Signal Service of the Army. 

417.— Joints. Where wires have to be joined to preserve the 
continuity of the metallic circuit, the best joint is the American 
twist joint. To make this clean the wires for a length of 5 or 6 
inches, make a right-angle bend in each wire about 4 inches from 
the end, now join the wires so that the ends project on different 
sides and clamp both wires with a hand vise, then with a splicing 
iron turn the ends around the line wire, making the turns as close 
as possible; after the entire end is turned around the line wire, 
cut off the projecting end and dip the joint into melted solder; 
this protects the joint against rusting. The details of this 
joint-making are shown in Figs. 7 and 8. 

418.— Military lines are generally of the kind designated as 
flying lines— i. e., they are intended to accompany the army in 
the 'field, are constructed quickly for temporary use, and are as 
quickly dismantled and taken up. The poles used are small poles 
called lances, each about 2% in. in diameter and 17 ft. in length, 
placed 2 ft. in the ground, and run about 40 to the mile. The 
batteries, line lances, and instruments are carried in wagons 
which accompany the army. A detailed description of the tele- 
graph, with directions how to erect and dismantle, is found in the 
Manual of Signals for the U. S. Army. The ordinary telephone 
receiver (with magneto call bell) is used on the military lines; but 
for the use of outposts, reconnoiterers and scouts a special form 
of telephone cart and wire has been adopted, the following de- 
scription of which is taken from the Report of the Chief Signal 
Officer of the Army, 1892: 

"The frame of this cart is constructed of bicycle tubing, and 
30 in. bicycle wheels with heavy cushion rubber tires are used. 
The cart is fitted with an automatic spooling device for reeling 



Telegraph and Telephone Lines. 189 

up the outpost cable. This device was made by F. S. Caliill & 
Co., and is a success. The cart carries 5 reels of cable aud 1 reel 
knapsack for use in places where the cart cannot penetrate 
owing to underbrush, etc. As the extreme width of the cart, 
measured at the wheels, is only 26 in., it can follow any ordinary 
path through underbrush. The weight of the cart complete 
with spooling device, but without the reels, is only 53 pounds; 
when loaded with reels and reel knapsack, the total weight 
is 157 pounds. The cart is well balanced upon its axle by a 
device which permits the point of support to be changed to bal- 
ance the cart as the distribution of the weight is changed by 
the cable being run out. In connection with the reel cart a tele- 
phone kit is used, and by attaching the double connector of the 
kit to one on the frame of the cart the telephone is kept in cir- 
cuit and conversation can be kept up with the home station. 
The cart with its load can be easily drawn by one man, and by 
its use it will be possible to connect outposts with the main 
guard, or brigade with regimental headquarters, or brigade 
with division headquarters, in a few minutes of time. The ex- 
perience of the English in Egypt has proved the value of the 
field cable line in action, as by means of these lines the Com- 
manding General was kept in communication with different 
divisions of troops and with those actually engaged in the firing 
line. It is proposed to fit shafts to the cart so that a horse can 
be harnessed to it, thus securing great rapidity in running out 
the cable. The cart carries 1 2-3 miles of cable, which can be paid 
out as fast as a man moves with the cart, and by means of the 
reeling apparatus and spooling device can be recovered at the 
rate of 4 miles per hour, or as rapidly as a man can walk with 
the cart." 

419.— Faults are generally of three kinds— breaks or discon- 
nections, leaks or escapes, and crosses or contacts. 

Breaks or disconnections occur when the metallic circuit is 
broken cr cut so that either the disconnection is complete, as when 
entirely severed; or incomplete, when partially cut or where a joint 
is rusted so much as to increase the conductive resistance. In 
these cases the instruments will work weakly or fail entirely. 

Leaks or escapes. Where the insulation is destroyed or is 
defective, of where a wire comes in contact with a conductor to 



190 Telegraph and Telephone Lines. 

the earth or with the earth itself, a portion of the current leaks or 
escapes. When the wire is swinging, the leak will be intermit- 
tent; when constant leakage is going on, the instruments will 
work weakly; when the leak becomes complete, failing altogether, 
it is called "a ground." 

A cross or contact occurs when two wires, each carrying cur- 
rents, are brought into contact; thus the instruments on one line 
will interfere with the workings of those on the other. Generally 
occurs from parallel wires being swung over one another by 
the wind, or having a good conductor fall so as to touch both 
wires. 

420. — Telegraph lines should never be damaged or destroyed, 
except in obedience to direct orders. Faults may be made by 
connecting the wires together with small wire (this makes a bad 
cross), or they may be connected with the lightning rods on the 
poles, thus running them to the ground. 

When an office is taken, the instruments should all be discon- 
nected and destroyed or taken aw T ay; the ends of the wires should 
be tied together. The batteries, if any, should be disconnected. 
To destroy the line, cut down the poles and burn them and cut 
the wire into small lengths. Subaqueous lines should be brought 
up with a grapnel and a piece cut out and cut into small 
pieces and thrown back into the water. Subterranean lines are 
generally laid in conduits, and at regular intervals man-holes 
are built to allow of repairs; the line may be detected by these 
man-holes, the conduit destroyed, and the cables disconnected. 



CHAPTER XX.— Demolitions. 

421.— In military operations demolitions must be made with 
the least possible expenditure of time and explosive. Neverthe- 
less, a charge which in itself seems large for the object intended 
may prove economical, in that it errs on the right side and a repe- 
tition of the work is not made necessary. 

Military engineers, or troops acting as such, may have to de- 
stroy bridges, houses, walls, railroads, tunnels, stockades, pal- 
isades, gates, cannon, etc., break up roads, fell trees and place 
mines. On account of their portability, great destructive effect 
and facility of handling, high explosives should generally be 
used in all these operations. However, where ordinary gun- 
powder is available, it may be used to advantage, if time permits 
its proper placing and tamping. Gun-cotton is the standard 
explosive for military work, and all formulas are calculated for 
its use. 

422.— Gun-cotton, as made at the U. S. Naval Torpedo Sta- 
tion, is in blocks about 3 Jn. square and 2 in. thick; each block 
is perforated to allow the insertion of a detonator, and, when dry, 
weighs about 10 oz. When necessary to use a smaller amount 
than 10 oz., a block may be cut, when wet, by using a saw or 
sharp knife, care being taken to place it between two boards, so 
that it will not flake or crack during the operation. 

Gun-cotton, as furnished by the U. S. Ordnance Department, 
is in small rectangular blocks weighing about 1-8 oz. The blocks 
contain about 15 per cent of water, are coated with varnish, 
and can be shipped or handled with safety. For use, a paper 
or cardboard cylinder is made and the blocks placed in it. The 
detonator Js inserted in a prepared primer, which is placed be- 
tween the blocks. 

Gun-cotton will absorb about 30 per cent of its weight of 
water, and, when in this condition, is comparatively safe, as it 
can only be ignited by lire and is difficult of detonation. When 
packed for transportation the blocks are placed, while wet, in 
a tin can; the can is hermetically sealed or is left so that the water 
can be replaced when it has evaporated. 

When both are well tamped, gun-cotton has an explosive force 
-13- 



PLATE 55. 



Figure 1. 

mm 



Figure 2 . 



i 



/ / /..* 




Figure 



Figure 4. Figure 



Figure' 
8, 




Demolitions. 193 

two times as great as gunpowder; when no tamping is used, it 
has a force four times as great. 

423.— Primers. Wet gun-cotton detouates with much greater 
force than dry, but it is necessary that this action be set up by 
the detonation of a dry primer of gun-cotton placed in intimate 
contact with the wet charge. AYhen wet gun-cotton is carried, a 
sufficient quantity for a primer may be taken from the wet case, 
placed in the sun and allowed to dry; it is better, how T ever, in 
operations in the field, to carry a small amount of dry gun-cotton, 
so as not to waste time in drying the primer. 

When used in holes, gun-cotton should be dry, as wet gun- 
cotton is difficult to detonate under such circumstances. 

424.— Dynamite. Dynamite comes in cartridges or sticks 
weighing 8 oz. each, and may be used instead of gun-cotton. It 
should not be used, however, if exposed to w T et or if frozen. 
Frozen dynamite can be thawed by placing it in an apparatus 
like a glue pot, the dynamite being in the inner vessel and the 
hot water in the outer. It must not be thawed at a fire. 

Gunpowder may sometimes be used in demolitions, and w T hen 
so employed it should be placed in stout bags, preferably two, the 
outer one well tarred. This is to protect from accidental explo- 
sion occasioned by sparks from the fuse. 

425.— Explosives should be placed in as close contact as pos- 
sible with the object to be destroyed, and the packages compos- 
ing the charge should be in intimate contact with each other. 

426.— Common Detonator. The common detonator is a cop- 
per tube, about % in. in diameter, closed at one end and partially 
filled with fulminate of mercury, which is ignited by a fuse. 
The ordinary blasting cap (PL 55, Fig. 1), or detonator, is in- 
tended for use with a fuse, and is designated as single, double, 
or triple force, according to the amount of fulminate of mercury 
used. In military operations it is better to use the triple- 
force caps, as their action is sure, even on comparatively low 
explosives.* 

427.— The fuse generally used in this country to ignite these 
detonators or caps is that made by Ensign, Bickford & Co., 
Simsbury, Conn., the grade known as "double-taped" being the 



♦Single-force caps contain 3 grs., double-force caps 6 grs., and triple-force caps 
9 grs. of fulminate of mercury. 



194 Demolitions. 

best for general work when the fuse is not exposed to pro- 
longed immersion in water or damp ground. When il is nec- 
essary to use fuse for submarine explosives, the water-proof 
fuse should be used. The rate of burning of the fuse should 
be found by experiment before using. This is .done by taking 
several pieces, 1 ft. long, and finding the average rate of burn- 
ing and taking this as the standard. The rate at which this fuse 
is intended to burn is 3 ft. per minute, but it varies somewhat, 
so that when great nicety is required it should be tested as 
above. 

428. — To prepare a fuse and detonator for use, cut the fuse to tht 
length required, leaving a square end; insert this end in the det- 
onator until it rests against the fulminate, taking care not tc 
scratch the fulminate. Then crimp the copper against the fuse so 
as to hold it firmly: this is done by means of pincers made for the 
purpose; or, in case these are not available, any pincers or the 
edge of a dull knife may be used, being careful not to crimp on 
the portion of the cap containing the fulminate. 

To fire gun-cotton, insert the detonator in the hole in the prim- 
ing-block, secure it by tying with wire or twine, and when ready, 
light the fuse. 

To fire dynamite, a hole is made for the detonator in the end 
of the cartridge with a sharp stick or lead pencil and the deto- 
nator, with fuse or wire attached, is inserted; the envelope is then 
tied around the fuse, so that the detonator cannot become de- 
tached from the cartridge, care being taken to place the deto- 
nator in the cartridge only about % its length, so that the charge 
may not be ignited by sparks from the fuse before the detonator 
is exploded. 

To fire gunpowder (PL 57, Fig. 5), the fuse alone is used, being 
placed so that the end is well centered in the mass of the powder 
and so secure that it cannot pull out. 

429.— The simple electric fuse is so constructed that, upon 
the passage of a current of electricity through a platinum wire of 
sufficient strength to heat the wire to redness, some fleecy gun- 
cotton or other inflammable material, which is wrapped around 
the wire, is ignited. This fuse may be used to fire a detonator or 
to ignite gunpowder. 

In PL 55, Fig. 2, is shown a fuse with a cap, which cannot be 



PLATE 56. 



FIG 1 




FIG 4 . 




FIG.6 \ 



w "t>i 



196 Demolitions. 

removed, containing a detonating compound; hence it can be used 
with best effect only in compounds that can be detonated. It is 
called the commercial fuse and detonator. 

In PL 57, Pig. 10, is shown a fuse with a cap containing a det- 
onator. The cap can be removed and the fuse used to ignite 
gunpowder. It is called the service fuse and detonator. 

Gun-cotton and gunpowder are fired as explained in Par. 428. 

To fire dynamite, push the detonator in its full length and take 
two half-hitches, with wire, about the cartridges, so as to hold 
everything in place. (PL 50, Fig. 1.) 

430.— The Laflin and Rand Exploder, No. 3. The current 
of electricity is generated by means of a battery consisting of 
several cells, or by an electrical machine. The means now gen- 
erally used, and the one that gives surest results,. is the magneto 
machine. On account of its compactness, portability, and sim- 
plicity, the Laflin & Rand Exploder, No. 3, is probably the best 
for all work where electricity is to be the igniting agent. (PL 55, 
Fig. 3.) The machine is cased in wood, and its dimensions are 
13x8x5% in. It weighs 18 lbs. The machine will fire, under 
favorable circumstances, 12 fuses. In order that there may be 
no chance of failure, a greater number than 5 should not be fired 
in military operations by this machine. 

The insulated wire used to make connection between the 
machine^ and fuse is carried on a reel, Fig. 3. The connecting 
wires between machine and reel are attached by binding posts, 
as shown in the figure. 

To use the machine, reel off a sufficient amount of wire, usually 
about 250 ft., and connect with the wires of the detonator; con- 
nect the machine with the reel, being careful not to make this 
connection until every one is at a safe distance from rRe place of 
explosion. The handle on top of the box is now lifted, with- 
drawing the ratchet bar to its full length, and, when the time 
arrives to fire the charge, the bar is pushed vertically down- 
ward, moving slowly for the first inch or two, then by a rapid 
but even pressure, till the lower end is stopped at the bottom of 
the box. 

When more than one charge is to be fired, the wires leading 
to the several charges should be connected, as shown in PL 57, 
F!g. 6. 



Demolitions. 197 

431.— In all connection of wires, at least 2 in. of each wire 
must be cleaned bright and well wrapped around one another, 
as shown in PL 55, Fig. 4; under no circumstances simply hook 
wires together. After wires are joined, the joint should be in- 
sulated by winding rubber tape, or wide rubber bands, around 
so as to overlap the next previous turn. When water has to be 
encountered, wrap with rag or a strip of linen and cover with 
tar; or, use rubber tube as shown: the tube in this case is placed 
on one of the wires, and, when the joint is made, is pulled over it 
and tied tightly to the wires on either side of the joint. (PL 57, 
Fig. 9.) 

432.— To fell trees, bore a hole at the height desired, insert 
the charge, and fire, care being taken that the center of the 
charge is about the center of the tree. If the charge be of a 
length equal to or less than the diameter of the tree, the hole 
may be bored directly through; but if greater, then two or three 
holes, intersecting at the center, must be bored, thus putting the 
packages of gun-cotton in intimate contact, and requiring but 
one detonator. The charge may be calculated from the formula 
C=y% T 2 , in which C is the charge in pounds and T the diameter 
in feet. 

When time is not available to bore a hole, a necklace may 
he used. The charge may be calculated from the formula C=3T 3 
in which C is the charge in pounds and T the diameter in feet. 

Should the charge be placed or hung against the tree, the 
amount as given by the formula for a necklace must be increased 
one-fourth. 

To make the tree fall in a given direction a rope may be tied 
to it, hauled taut, and secured to another tree or strong stake. 

The above method of felling trees is more expensive than with 
the ax, and is not to be resorted to except in cases of emergency 
where time is not available for slower methods. (PL 55, Figs. 5, 
C>. 7 and 8.) 

433.— To destroy bridge timbers, if rectangular, the charge 
is placed across the whole width of the timber. (PL 56, Fig. 2.) 
The charge may be calculated from the formula C=3WT 2 , in 
which C is the charge in pounds. W the width and T the thickness 
In feet, If the timbers are circular or square, the formula re- 



198 Demolitions. 

duces to C=3T 3 , and being the same as that for trees where a 
necklace is used, the charge should be so placed. 

When high explosives are not on hand, the bridge torpedo used 
in the War of the Rebellion may be substituted. It consists of 
a bolt 8 or 9 in. in length, surrounded by a tin cylinder 2 in. in 
diameter, which is filled with powder. The ends of the cylinder 
are closed by iron washers, and a fuse placed in one end. To 
use this torpedo, a hole 2V 2 in. in diameter is bored in the timber 
and the torpedo inserted, having its center at the center of the 
timber; it is then exploded by means of a fuse. If necessary, 
two may be placed in holes bored at right angles to each other. 
(PL 56, Fig. 4.) 

434.— To destroy a wooden truss bridge, if time is available, 
the bridge may be burned; to do this, collect brush, etc., and, if 
possible, place it under one end so as to burn it off and cause the 
span to drop, but if not possible, build the fire in the center of the 
span; it will burn through and cause rupture in the center. If time 
is not available, blow away the main brace of the panel nearest 
to an abutment or pier; it is really necessary to blow only one side 
down, but it is better to be sure and destroy both sides. If the 
bridge has an arch of wood besides the truss, then destroy the 
arch on each side. It is better to attack the span over the deepest 
water. 

435.— Palisades may be cut down with axes or saws, the cuts 
being made near the bottom; ropes are attached to the tops of 
the timbers to assist in bringing them down; or the earth at the 
bottom may be dug out and the palisade pulled over. 

Palisades, up to 10 in. in thickness, may be blown down, when 
the timbers are close together, with 4 lbs. of gun-cotton per run- 
ning foot. 

436.— Stockades may be cut down with axes or saws, as ex- 
plained for palisades. 

They may be blown down with 4 lbs. of gun-cotton per run- 
ning foot. 

If the timbers are squared, the blocks of cotton may be fas- 
tened to a thin board "and placed against the foot of the stockade; 
but if. of rough logs, tie the blocks together so that they may 
adapt themselves to the form of the timbers. 

When stockades are double, and separated by a distance of 



Demolitions. 199 

one yard— 25 lbs. of gun-cotton per running foot or one charge of 
SO lbs. may be placed. 

Railway-iron stockades are breached by 7 lbs. per running 
foot. 

In all cases, distribute the charge so as to cover the length 
desired to be breached. 

437.— Gates may be blown in with 50 lbs. of gun-cotton ex 
ploded in one charge. The charge is hung against the center of 
gate by means of a sharpened pick or on a nail. This charge is 
large, but gates will generally be strengthened in some manner 
on the inside. (PL 57, Pig. 4.) The gates of Pekin were opened 
by a couple of shots from 3.2-inch field guns directed at the locks. 

438.— Houses may be blown down or shattered by placing 
charges in the center of the floor and closiDg all outlets, such as 
doors, windows, etc. Charge according to the size, 20 lbs. being 
sufficient for small houses. 

439.— Walls. The charge should be placed against the bot- 
tom, close to the wall, .and, if possible, should be tamped. If 
time permits, a channel may be cut in the wall at the seat of the 
charge. The charge untamped may be computed from the for- 
mula C=%WT 2 in which G is the charge in pounds, W the width 
of wall to be breached, and T the thickness; W and T are in feet. 
When tamped with earth equal to the thickness of the wall, half 
the above charge may be used. (PL 57, Fig. 2.) 

440.— Masonry bridge piers may be destroyed by a charge 
calculated from the formula C= W T - , C, W, and T being the 
same as in par. 439. In order to avoid using so much gun-cotton, 
it is better to place small charges in chambers excavated as deep 
as possible in the masonry, and explode all simultaneously; cal- 
culate charges as for walls. 

441.— A masonry bridge arch may be destroyed by attacking 
the haunches or the crown. The haunches are the best points of 
attack, two trenches being dug across the width of the roadway 
down to the back of the arch. If this is not possible, attack 
the crown. A single trench across the width of the roadway 
may be used, but it is better to use two, each placed from the 
crown a distance equal to one-half the width to be breached. The 
charge untamped may be calculated from the formula C=%WT -. 
in which C, W, and T are the same as in par. 439. When the 
charge is tamped with a depth of earth equal to the thickness of 



200 Demolitions. 

the arch, one-half the amount given by the formula is used. (PL 
57, Fig. 3.) 

442.— Tunnels may be destroyed by placing charges back of 
the masonry at the spring of the arch. If possible, the charge 
should be placed in a chamber excavated behind the arch and 
well tamped. Tunnels should be blown in at several places, so 
as to render it impossible to repair them in a short time. Charges 
as for bridge arches. (PL 57, Fig. 8.) 

443.— To cut steel rails, use one block of gun-cotton, weight 
8 ozs., tie the block against the web of the rail with wire or twine, 
and, if possible, tamp well with earth, and explode. (PL 56, 
Fig. 8.) 

To blow a piece of some length out of a rail, arrange two 
charges of 8 ozs. as shown in Fig. 5, placing one on each side of 
the rail at a distance apart of 5 or 6 ft.; these should be exploded 
by use of a magneto machine, so that the action may be simul- 
taneous in both charges; the section will be blown out and turned 
on its center, making a large opening. 

444. — Switch points may be destroyed by lodging 8 ozs. of gun- 
cotton between the outer rail and the pivot end of the switch 
point, being careful to tamp as completely as possible. ("A," PL 
51, Fig. 11.) In the case of frogs, 8 ozs. placed in the angle of the 
frog will destroy the point and render it useless. ("A," PL 52, 
Fig. 1.) 

A great length of railway may be disabled at a very rapid 
rate by making use of hand-cars loaded with gun-cotton, pre- 
pared lengths of fuse inserted into detonators, torches, and 
copper wire for binding the gun-cotton to the rail. One non- 
commissioned officer and seven men will be necessary; two run 
the hand-car; two sit on the hand-car and fix the detonators to 
the gun-cotton, prepare binding wire and hand out the charges: 
two men receive the charges and bind them to the rails; two 
follow at about 150 yards in rear and fire the charges as they 
pass. 

445.— To cut wrought-iron plates, the charge is found from 
the formula C=1.5Wt*. in which C is the charge in pounds, W the 
width in feet, and t the thickness in inches. The charge should 
be placed entirely across the plate to be cut. 

446,— To cut etn iron bridge l?eajn or girder (PI. 56, Figs. 6 



Demolitions. 201 

and 7), calculate the charge for each separate cross-section to 
be cut, using the formula in par. 445, and add the results; the 
sura will be the charge required. The charge is most conven- 
iently placed on the side of the beam, reaching entirely across 
and bound on with wire, the primer being in the center of the 
charge. If possible, a board should be tied over the charge and 
earth tamped around it. When time is not available for placing 
the charge as above described, it may be laid on top of the beam 
or on the flange. 

447.— Girder bridges not longer than 20 ft. may be overturned 
by levers and thrown off the abutments. When this cannot be 
done, the gun-cotton charge may be calculated and placed as de- 
scribed for iron girders. 

448.— In iron truss bridges the most favorable place for the 
charge is at the center of the span on the lower chord. When 
the bridge is of the variety known as a deck bridge, the charge 
should be placed on the top member. When the lower or ten- 
sion member is composed of eye-bars, the charge should be placed 
between alternate pairs of eye-bars as near to the coupling- 
pin as possible. The charge may be calculated as in par. 446. 
(PL 57, Fig. 1.) 

449.— When bridges are supported by iron or wood piers, it is 
sometimes possible to destroy the piers, and thus bring down the 
entire structure. In attacking a pier, it is best to blow out the 
supports on both sides, as this will bring down all of the bridge 
resting on the pier. The charges may be calculated, if of stone, 
by par. 440; if of iron, by par. 445. 

450.— In destroying suspension bridges, blow down the tow- 
ers below the saddles, excavate and blow out one of the an- 
chorages, or cut the cable with gun-cotton. The charge for 
bridge cables is calculated as for cutting iron plates; the charge 
must be carefully placed, so as to be in close contact with the 
cable. If the cables are made of plates, the plates may be cut 
with gun-cotton, as in the case of eye-bars cited above. 

451.— Field and siege guns may be disabled by detonating 
iy 2 pounds of gun-cotton on the outside near the muzzle. For 
heavier fortress guns, detonate 4 pounds in the bottom of the 
bore, tamping with sand. The carriages may be destroyed by 
using gun-cotton, 



PLATE 57/ 



i — i 



1 


^^ ■ -,nu. j 


L. 






< 


< 


1 1 


> 






< 


s 



FIG. 2. 



FIG.3. 





FIG. 4 




FIG. 6. 



C 



FIG 10. «.,W.f« 



>;■: 




copper case, 
houow wood cap. 



t. 

c.c wires, .035 
cL ortdtge 
■f. printings 

h. fulminate of mercury, 
10 to 0,4 grains. y 

A. plug of beechwood 



FIG. 9. 



Demolitions. 203 

452. — Approximate Relative Strength of Some of the High 
Explosives. 

Explosive gelatine 128.3 

Nitro-glycerine ..120.3 

Gun-cotton 100. 

Dynamite, No 1, 75 per cent Nitroglycerine 97.8 

Rack-a-rock 74.2 

Dynamite, 50 per cent 72.7 

453.— Destruction of Obstacles. Wire entanglements may 
be destroyed by cutting with wire nippers, or, if they are not at 
hand, then the ordinary hand-ax will do, taking care to cut against 
the picket. 

Abatis is very difficult to destroy and cannot be removed 
while fire can be brought to bear on the spot. Pry up the pick- 
ets with levers and attach ropes to the butts of trees and haul 
away. 

Small pickets are cut through with the ax, or, if possible, 
pulled up. 

Small pits are filled with earth, brush, or covered by planks, 
fascines, or bales of hay. 

Automatic torpedoes are easily destroyed by driving animals 
up and down the line suspected of containing thein. 

454.— The following table gives in a concise form all informa- 
tion necessary for the use of gun-cotton and gunpowder. The 
table shows approximately the value of the different high explo- 
sives as compared with gun-cotton. 

NOTE.— Charges are in lbs.; W and T are in feet; t is in inches. 

W is width of breach to be made; T or t is thickness of object 
to be demolished. 

Gunpowder is assumed to be roughly tamped with sand-bags. 
Gun-cotton is untamped. If the gun-cotton is tamped, the charges 
may be reduced by about one-half. 

Charge of gun-cotton must be equal in length to the breach 
which is to be made. 



204 



Hasty Demolitions. 



Object Attacked. 



Gunpowder 



Brick arch -\ 

Brick wall, 2 ft. or 
less 

Brick wall over 2 ft. 
thick. 

Brick piers ... 

Hardwood (e £\,oak, 
elm), in any form, 
whether stock- 
ade, palisade, sin- 
gle timbers, trees, 
etc. 



|WT 2 i 



40 to 100 
lbs. for 
stockade 



Soft wood 



Breastwork of hori 
zontal balks, or 
earth between 
sleepers up to 3 ft. 
6 in. thick 

Heavy rail stockade 



Fortress gate 
Iron plate 



Field or siege guns 
Heavier guns 



First-class iron rail. 
First-class steel rail. 



Half the 
for hard 

60 to 80 
lbs. per 
5 ft. 



200 lbs. 



Gun-cotton 



JWT 2 

2 lbs. per 

foot run 

|WT 2 
|WT 2 
3WT 2 



IT 2 



charges 
wood. 
4 lbs. per 
foot. 



7 lbs. per 
foot. 
50 lbs. 
fWt 2 

14 lbs. 

4 lbs. 



10 ozs. 



8 ozs. 



Remarks. 



The length of 

breach, W, should 

ynot be less than the 

height of the wall 

to be brought down. 

In a concentrated 
charge, or for trees 
not over 12 in. diame 
ter, in a necklace. 

In auger-hole, when 
the timber is not per- 
fectly round, T= the 
smaller axis. 



In this case only, t 
is in inches. 

On chase near muz- 
zle. 

In bottom of bore, 
tamped with water or 
sand. 

Touching web of 
rail and near a chair. 

Four rails placed 
round the charge will 
be cut simultaneously 
by it. 



CHAPTER XXI.— Camping: Expedients. 

455.— There are a few general principles which should be ob- 
served in selecting a camp, whether the troops are to be estab- 
lished in bivouac, in tents or in huts. These principles relate to 
the health and comfort of the troops, the facilities for communi- 
cation, the convenience of wood and water, and the resources of 
the locality in provisions and forage. 

456.— For an intrenched camp the ground must be selected 
with particular reference to its adaptability for defense and the 
camp arranged with that object in view, at the same time observ- 
ing as many of the other requirements as possible. 

457.— Dry and healthy sites, dependent on soil: Granite, 
metamorphic and trap rocks, usually; clay slates, but drinking wa- 
ter is scarce; limestone generally, but the water is hard, clear 
and sparkling, though sometimes contaminated; deep permeable 
sandstones, if the air and soil are dry; deep gravels, unless lower 
than surrounding country; pure sand, deep and free from organic 
matter; well-cultivated soils generally; gravelly hillocks, the very 
best. 

458.— Unhealthy sites, dependent on soil: Magnesium lime- 
stone; shallow sandstone underlaid with clay; clay and alluvial 
soils generally; rice fields; made soils usually; newly plowed 
ground. 

459.— Healthy sites, independent of soil: The best is on a 
divide or saddle, unless too much exposed or without water. The 
next best is near the top of a slope, and the southern side is prefera- 
ble to the northern; banks of running rivers are good, if not 
marshy. 

460.— Unhealthy sites, independent of soil: Enclosed valleys, 
ravines, or tlw mouths of long ravines, ill-drained ground, the neigh- 
borhood of marshes, especially if the wind blows from them. If 
forced to camp near a marsh, the windward side should be select- 
ed, and, if possible, have a hill or a screen of woods or brush be- 
tween the camp and marsh. Moss generally indicates marshy 
ground. 

461.— Sites affected by surrounding vegetation: Herbage, 
or closely lying grass, is always healthy, but should be kept 



206 Camping Expedients. 

cut and all weeds destroyed; heavy brush about a marsh should 
not be removed. Trees, in cold countries, break the winds; 
in hot countries they cool the ground and may protect against 
malarial currents; so should only be removed with judgment. 

462.— In selecting camps, wood, water, and grass should be 
secured, if possible, together with good drainage, but marshy 
ground should not be occupied even for a night. 

Old camp-grounds should never be occupied, if avoidable; 
instead, go as far as possible to the windward side of them. 

The site having been selected, the details of castrametation, 
or the laying out of camps for the different arms, will be found in 
the authorized Drill Regulations of each. 

463.— Water is more immediately necessary to life than 
food. 

Each -man requires, in bivouac on the march, for drinking and 
cooking 3 to 4 quarts per day, and an- equal amount for washing. 
In camps, 5 gallons per day for all purposes. 

Hospitals require several times as much per man per day. 

Horses, mules, and cattle require from 6 to 10 gallons each 
per day for drinking. It should be soft and clean, if possible. 
Sheep and hogs require from 2 to 4 quarts each per day. 

464.— J£ is imperative, on going into camp, that the supply be imme- 
diately looked after and a gimrd placed over it. If the supply be 
small, special precautions must be taken and an officer put in 
charge. 

465.— Good drinking water should be bright, colorless, odor- 
lees, free from sediment, of pleasant and sparkling taste. 

Rain water, collected from a clean surface, after the atmos- 
phere has been well washed, is the purest in nature. Springs 
whose origins are remote from habitations, streams flowing 
through uninhabited regions, and large lakes, furnish the next 
best sources of supply. 

466.— Tf the supply be from a lake, pond, or stream, separate 
places for obtaining water for men and animals must be marked 
out, and care taken that the margin is not trampled into mud and 
the water made turbid. Where this is likely to occur when ani- 
mals are watered direct from the source of supply, a hard bottom 
should be formed for them to stand on, and a barrier formed to 
prevent them going out too far. 



Camping Expedients. 207 

It is better, when convenient, to arrange rows of sunken half- 
barrels, or board troughs raised above the ground, into which the 
water can be drawn. If the supply be limited, it may be neces- 
sary to connect the troughs to prevent waste; if not limited, each 
should be supplied direct from the source and the overflow 
drained olf. Even when drinking from a running stream, the 
animals below get foul water. To prevent the ground around the 
troughs becoming muddy, it should be paved and drained along 
the whole length and for a distance of 10 or 12 ft. back. Where 
troughs cannot be constructed, trenches lined with puddled clay 
may be made to answer. 

Arrangements should be made so animals may be brought up 
from one direction and leave in another without confusion or 
crowding. 

467.— If the supply be from a stream, the water for drinking 
and cooking for the troops is drawn highest up; for the animals 
to drink, next below; and for washing, bathing, etc., lowest down; 
while all drainage should enter below where any water is 
taken. 

If the stream be small, it may be necessary to construct a 
series of small reservoirs by building small dams across. Ani- 
mals drink better and more rapidly where water is 5 or 6 in. 
deep. 

468.— If unavoidable, water from small ponds and shallow 
wells should only be used after being boiled half an hour, then 
aerated and filtered. In fact, the only safe method of treating any 
water that is not known to be pure is to boil it thoroughly for at 
least half an hour, or distil it, one or the other of which methods 
should always be insisted upon. 

469.— If the supply be from springs, each should be enlarged 
and surrounded by a low puddled wall, to keep out surface drain- 
age. They may be lined with casks or barrels charred inside, or 
gabions, afterwards working in puddled clay between the earth 
and linings. The overflow may be received into a succession of 
casks let into the ground close together. 

Surface springs should be sought for in hollows, at the foot 
of hills, where the earth is moist, the grass unusually green, or 
the thickest mists arise mornings and evenings. 

470.— If water is not immediately available, it may be neces- 
-14- 



208 Camping Expedients. 

sary to dig wells. The most expeditious means of doing so is to 
use Well Augers. (PI. 58, Figs. 1, 2, and 3.) 

471.— To dig a well, an auger is attacked to a rod suspended 
from a rope passing over a pulley at the top of a derrick or tripod 
and thence to a windlass. To the auger rod is secured an arm or 
arms, by which the auger is turned by hand and so screwed down 
into the earth. About eight turns fill the auger, which is then 
lifted, emptied and replaced. 

472.— The auger for boring in quicksand (Fig. 3) is shaped simi- 
larly to the ordinary wood-boring auger, but with a hollow shank, 
so that, when lifted, no suction is produced. When the thread be- 
comes loaded, the auger is drawn up into an enclosing cylinder, 
removed from well and emptied. 

473.— Driven wells. The driven tube-well consists of a tube 
about 3 ft. long, perforated with holes, and furnished with a steel 
point of bulbous form (Fig. 4) and as many other plain iron tubes 
as may be necessary. 

The form of the point serves to clear a passage for the sockets 
by which the tubes are screwed together. 

474.— To drive a well, a tube is screwed to the point (Fig. 5) 
and on this a clamp is fastened by two bolts at about 3 ft. from 
the lower extremity of the point. Next, an iron driving weight, 
or monkey, is slipped on the tube above the clamp. The tube thus 
furnished is raised and held vertically in the center of a guide, 
in which it is retained by a latch. The whole being now arranged 
in position, ropes are made fast to the monkey and passed over 
pulleys on the guide, and driving commenced by two men pull- 
ing the ropes and allowing the monkey to fall on the clamp. As 
soon as the clamp reaches the ground, the monkey is raised and 
held up, the clamp loosened and raised 1.5 or 2 ft., tightened, 
and the driving continued as before until the top of the tube 
comes below the hole in the top of the guide head, when the 
lengthening bar (Fig. 7) is dropped into the top of the well-tube. 
The lengthening bar consists of a length of the well-tubing with 
a smaller pipe brazed into one end and projecting about 1 ft., 
which fits into the well-tube. This bar keeps the tube steady 
and serves as a guide for the monkey to slide on until the top 
of the well-tube reaches to within a foot of the ground. The 
lengthening bar is then removed, another tube is screwed on, 



PLATE 58. 




210 Camping Expedients. 

and the driving continued until water is reached. A hollow 
iron plumb is frequently lowered into the tube to ascertain when 
water has been reached or whether earth of any kind has got 
into it. 

Accumulations in the tube, of a loose sandy nature, can be 
pumped up, by screwing a funnel (Fig. 8) on top of the tube, then 
lowering into it through the funnel a small tube with a pump 
attached. Water poured into the funnel runs down outside the 
smaller tube and is pumped up through it, bringing the mud and 
sand. When water is struck, and stands several feet in the tube, 
the pump is screwed on to the well-tube. 

The well can also be driven without the use of the tripod sup- 
ports (Fig. 6), care being taken to keep the tube vertical by means 
of guy-ropes. Such a well can be driven from 10 to 20 ft. per hour. 
The tubes can be withdrawn without damage by reversing the 
operations of driving. (Fig. 9.) 

475. — The tube-well is not intended for piercing rock, or 
solid stone formations, but is quite capable of penetrating very 
hard and compact soils. When striking rock, stone, or deep beds 
of clay, it is best to pull up the tube and try in another spot, for 
by going a little distance off water will in many cases be found. 

476. — Clarification of water. Water usually contains min- 
eral and organic substances in solution and in suspension. Sub- 
stances in solution completely disappear and cannot be entirely 
filtered out. Substances in suspension do not entirely disappear 
and may be filtered out. 

477. — Hard water contains one or more substances, as lime, mag- 
nesia, iron and otllers, in solution, which are liable to produce 
intestinal troubles to persons unaccustomed to them. Cooking 
vegetables in it is very difficult. Washing with it requires a 
great deal of soap. 

The hardness of water may be partially removed by boiling 
for half an hour or so, or by adding a small quantity of wash- 
ing soda, or by adding a couple of ounces of quicklime to 100 
gallons. 

478.-- Substances in suspension may be largely removed by pre- 
cipitation and filtration. 

479. — Precipitation is allowing such matter as will to settle 
through its greater specific gravity, or by inducing it to do so 



Camping Expedients. 211 

through some harmless chemical or mechanical action. For 
which purpose may be used about 6 grains of crystallized alum 
to the gallon, or tannin in small quantities, and letting stand sev- 
eral hours before using; bruised cactus leaves, also tea leaves 
that have been used, act similarly; citric acid, 1 oz. to 16 gal., or 
borax and alum, 1-3 oz. each, or 1 to 2 tablespoonfuls of ground 
mustard to a barrel, improves water. 

480.— Filtration is mechanically arresting and attracting sus- 
pended matter, and removing dissolved matter in the water. Fil- 
tering materials act only for a short period and should be fre- 
quently cleaned. 

481.— Materials wJiicfi may be used are sponge, wool, and like 
articles for straining, but must be constantly removed and 
cleaned. Clean sand, gravel, and porous stone remove sus- 
pended matter, but have little or no effect on dissolved organic 
matter. Iron sponge, a compound of sawdust and iron oxide 
heated in a furnace, and Car-feral, a composition of charcoal, iron, 
and clay, are efficient for removing mineral matter. Bone-black 
or animal charcoal, and wood charcoal, when freshly burned, ab- 
sorb mineral matter for a couple of weeks, but their chief action 
is on organic matter. 

482.— Charcoal may be made by digging in the ground a cir- 
cular pit some 6 in. deep by 4 or 5 ft. across, then placing a large 
pole or bundle of brushwood vertically in the center. Around 
this the wood to be burned is piled, forming a kind of cone. The 
pile is then covered with brush, and on this a layer of 4 or 5 in. of 
earth. (Fig. 10.) The center pole is then removed and a fire 
lighted in its place, receiving air from vents left at the bottom for 
that purpose. The fire proceeds from the center outwards, and, 
if burning properly, the smoke is thick and white. If it does 
not spread to every part, new vents must be made. If the smoke 
becomes thin and a blue flame appears, it is burning too fast, and 
vents must be stopped up or more earfh thrown on. When the 
smoke cpases to escane. the vents and chimney are closed and the 
pile allowed to stand for a couple of days until it cools. 

From 20 to 25 per cent of charcoal is thus obtained. 
483.— A convenient portable filter (Fig. 11) is made by 
taking a small cylinder of compressed carbon and inserting it 
in a rubber tube in such a manner that the carbon end may 



212 Camping Expedients. 

be immersed in the water, then applying the mouth to a mouth- 
piece at the other end of the tube, and drawing the water through. 

484. — The Success Filter (Fig. 12) consists of a cylindrical 
porous stone 4 in. long by 4 in. in diameter with a hole bored in 
one end. In this is fitted a rubber gasket, through which passes 
an iron tube that is fastened into the bottom of a barrel, jar, or 
bucket. The water filters through the stone into the hole inside 
and passes out through the tube into a receiving vessel below. 
(Fig. 13.) 

By fastening the iron tube into the bottom of a large empty 
tomato or peach can, in which the stone is placed on the tube and 
wedged fast, then fastening a rubber tube 2 or 3 ft. long on the 
iron tube outside of the can, a syphon filter is obtained. The 
action is set up by exhausting the air from the stone, after the 
can and stone are immersed in water, by sucking on the end of the 
rubber tube until the water is started. 

485.— A simple water filter may be made by stuffing a 
piece of sponge in a hole in the bottom of a cask, flower pot, or 
other vessel (Fig. 14), then placing above this a layer of coarse 
sand, then a layer of pounded charcoal 3 or 4 in. thick, then 
another layer of coarse sand and on this a layer of coarse gravel. 
The layers should be thick as possible, and tightly compressed, 
and washed thoroughly clean before being used. The differ- 
ent layers may be prevented from mixing by perforated boards, 
or otherwise. Another form may be made as shown in Fig. 15. 

486.— Casks, or barrels, charred on the inside (and occasionally 
cleaned, brushed, and recharred), improve water. 

487. — Latrines. Arriving on the site of a camp, one of the 
first duties is to designate the places to attend to the calls of na- 
ture, and there dig latrines. Urinals should be placed nearer the 
camp and of easy access. 

The only exception to digging latrines is when the command 
is very small, is certain to march the next day, and no other 
troops are to follow. 

488.— Latrines and urinals should be so placed as not to be in 
the course of the prevailing winds to the camp, and must be so 
situated that they cannot pollute the water, either directly or by 
soakage, 



Camping Expedients. 213 

489.— A small, shallow trench will suffice for a single night, 
and should invariably be filled in the morning before marching. 

For longer periods, a trench 2 or 3 ft. wide at top, from 2 to 10 
ft. deep, and 12 to 15 ft. long for every 100 men, should be dug, 
throwing the earth to the rear, from which a layer of a few inches 
should be thrown into the trench every day, or oftener if neces- 
sary. Lime or charcoal may also be used to deodorize the 
soil. 

It is better to increase the number of trenches than to make 
any one trench too long. 

Shallow latrines should be discarded when filled within a foot 
of the surface, and completely filled in with earth; deep ones when 
within 3 or 4 ft. of the surface. 

All latrines should be filled in and marked before marching. 

490.— In temporary camps, latrines may be provided with seats 
of a pole and a back, and be screened by bushes, canvas, or other 
means. (Fig. 16.) 

491.— Kitchens. On going into camp, kitchens should be 
promptly established, and in the same relative positions as if the 
camp were going to last a month or more. A pit should be dug 
near by for strictly liquid refuse, while solid matter should be 
placed in a box or barrel for the police party to remove. 

4:92.— When fuel is plentiful, el trench of sufficient length and 
about 1 ft. deep may be dug to contain the fire, over which the 
kettles are hung from supports. (PL 59, Fig. 1.) 

If fuel is scarce, then dig a trench as above in the direction of 
the wind, but a little narrower than the diameter of the kettles to 
be used. Place the kettles over the trench and fill in between 
with stones, clay, etc., forming a kind of flue. The draft may be 
increased by building a chimney of sods, stones, etc., on the lee- 
ward end and enlarging the windward end. (Fig. 2.) 

If the camp is to be for a long time and the direction of the 
wind liable to vary, a number of such trenches may be dug 
radiating from a common point, over which point a chimney is 
constructed. Then, whatever the direction of the wind, the 
trench opening in that direction can be used, the others being 
closed. 

The trenches should have a slight fall from the chimney back 
for drainage, and a means for the water to escape. If the ket- 



PLATE 59. 



FIG.l 



FIG.2./k 




£M 



Camping Expedients. 215 

ties are small or of various sizes, rests of stones, scraps of iron, 
etc., may be placed across the trench. 

A square hole may be dug for the fire with trenches for draught 
at the corners, the kettles being placed on rests over the fire. 
(Fig. 3.) 

493.— A ijrillaye or kind of grate about 1 ft. high, made of gas- 
pipe or bar-iron, is sometimes used to set over the fire, and on this 
are placed the kettles. (Fig. 4.) These are sometimes made with 
movable joints, so as to be closed for transportation. 

494.— If a covered kitchen is desired, either a trench similar 
to Fig. 2 can be dug, or one above ground can be built Avith stones 
and sods and a tent placed over it, or a cover constructed. 

495.— To bake bread, when none of the portable ovens of the 
Commissary Department are carried, improvised ovens must be 
constructed. The simplest method is to take a barrel with one 
head out (one with iron hoops best), lay it on its side in a hollow 
in the ground and then plaster over with wet clay 6 to 8 in. thick, 
then with a layer of dry earth equally thick, leaving an opening 
of 3 or 4 in. at the top of the closed end for a flue. The staves are 
then burned out by a hot fire, which also bakes the clay covering, 
forming an arched oven. To bake, after heating, the front and 
flues are closed. Or a pit may be dug from 6 to 12 in. deep and 4 
by 5 ft. for the hearth, over this form an arch with a hurdle or any 
other material available (Fig. 7), with a chimney at one end and 
a door at the other. Then plaster and cover the arch as in the 
barrel oven and bake the clay covering. 

496.— An oven may be excavated in a clay bank (Fig. 6) and 
used at once. 

497.— The Buzzacott Army Field Oven (Fig. 8), which is an ar- 
ticle of issue, is a complete camp cooking outfit, consisting of oven, 
baking and frying pans, etc. All are securely packed together and 
can be conveniently carried in the feed box of an army wagon or 
on a pack animal. To use it,*a bed of live coals is first obtained, 
then the oven after being heated is placed on rests over a bed of 
coals, and a layer of sand sprinkled evenly over the bottom of the 
oven to prevent burning out. In this is placed the pans of pre- 
pared food on suitable rests and the whole covered with a hood. 



216 Camping Expedients. 

On the hood is scattered a layer of live coals and burning brands. 
Broiling, frying, coffee-making, etc., may be done on top of the 
oven by using the remaining pans, rests, etc., at the same time 
that the interior is used for baking. 

498.— -Drainage. The camp being located, a system of sur- 
face drainage should be carefully traced and constructed. As 
soon as a tent is pitched it should be surrounded by a shallow 
ditch outside, emptying into a company ditch. The proper meth- 
od of doing this is to have the inner edge of the ditch come just 
inside of the skirt wall of the tent to catch the water running 
down the side of the tent and to drain the interior. 

The picket should be inside of the ditch. (Fig. 9.) To bank 
earth up against the tent soon rots the bottom of the wall. 

499.— Beds. The ground being generally too damp to lie upon 
directly, all should sleep upon some dry material, as straw, leaves, 
or preferably a low platform constructed of small branches and 
poles, if available. (Fig. 10.) 

If required to sleep upon the ground, one will sleep more com- 
fortably if he scrapes out a small hollow for his hips. Straw, 
hay, etc., for sleeping upon may be made into mats with the Malay 
Hitch as in Fig. 11. 

500. — Windbreaks. When troops bivouac, some protection 
from wind may be obtained by building up to the windward a 
pile of earth, sods, etc. Where trees are available, by resting a 
pole on two forked sticks, 4 or 5 ft. high, against which branches, 
thick end up, are piled at an angle of 45° on the windward side. 
(Fig. 12.) Hurdles similarly placed, supported and covered (Fig. 
13), canvas or blankets secured as in Fig. 14, straw or hay clamped 
between poles as in Fig. 15, may be used. 

By throwing up either a half or whole circle of earth 18 ft. in 
diameter, from a ditch on the outside, some protection may be 
obtained. On the bank so formed additional windbreaks may be 
placed or a covering extended over it all may be made. (PI. 60, 
Figs. 1 and 2.) 

501.— In cases of prolonged occupation, if tents are not avail- 
able, the troops sboitlfl buJlfl shelter of some kind, 



PLATE 60. 





_J~ L_ 




< -7/W 


f\ i"**V 




j : 






218 Camping Expedients. 

Huts may be built of timber, logs, brushwood, adobe, etc., in 
connection with straw, bark, sods and similar materials. 

All huts should, if possible, have their floors raised above the 
ground to allow free circulation of air underneath. (Fig. 3.) Only 
in very dry soil and when not to be occupied long is it allowable 
to sink them, if avoidable. Space between huts in the same row 
should equal the height of walls, and passage in rear equal the 
height of ridge. Hut sites should be well pounded. 

Huts are ordinarily constructed to contain a small number of 
men, but the sizes and details of construction will depend greatly 
upon the site and materials available. 

A very fair minimum allowance per man of bed space is about 
2.5 ft. x 7 ft. with a passage at foot from 2 to 4 ft. 

Thus, the plan for 8 men may be taken at 10 ft. x 18 'ft., ar- 
ranged as in Fig. 4. For 12 men, 15 ft. x 18 ft. For 16 men, 20 
ft. x 18 ft. For 20 men, 25 ft. x 18 ft. 

For calculating the accommodation at the above rates, allow 
1 man per pace of length for a single row of beds and 2 men per 
pace of length for a double row of beds. 

502. — Major Smart, Medical Department, recommends as best 
a modification of the Army of the Potomac hut, of rectangular 
plan (Fig. 5), 7 ft. x 13 ft., height to eaves 6 ft., to ridge 10 ft.; door 
in middle of one long side, chimney opposite door on outside of 
wall; on each side of doorway a double bunk. This hut to accom- 
modate 4 men. 

If logs are used, the ends are trimmed with an ax where they 
lap at the corners, so they will lie one upon the other throughout 
their length. 

503.— If made of small timber, some style, as in Fig. 6, with 
thatched roof, might be used. 

If, for any reason, it is not desirable to build huts as above, 
forms may be used as shown in Fig. 7, or hurdles, as in Fig. 8. 

504.- Sentry boxes may be made as in Fig. 9, the side cover- 
ing consisting of watling described in Chap. IX. and the roof 
thntched. 

505. — An excellent form of bamboo hut with grass roof, as 
shown in cut, has been successfully usied in the Philippines. The 



Camping Expedients. 



219 



corner posts were made double for additional strength, the floor 
being of bamboo strips lashed firmly to bamboo floor beams. 
Wooden pins and rattan lashings were used throughout. The hut 
shown is 16 ft. square, in the clear, and furnished comfortable and 
sanitary sleeping-room for eight men on gold medal cots. 




INDEX. 



Par. 

AB AT IS , consists of, how 

made 50 

in shallow ditch, of small 
branches, in front of 

glacis 51 

how destroyed 41 

ADVANCE D PO s C\ rear of. . . 204 
ANCHORS, number of, scarc- 
ity of 343 

substitutes lor 344 

use of 342 

weights of, names of parts 

of 341 

ANGLE, equal to a given 
angle, method of laying 

out 22 

right, method of laying 

out 18 

re-entrant, salient, shoul- 
der 82 

APPROACHES, in siege oper- 
ations constructed by 

infantry 154 

AREA, of rectangle, of trape- 
zoid, of triangle, method 

of finding 25 

ARTILLERY, in defense of 

village, where placed... 215 

in woods 179 

projectiles 9 

to be placed outside of 

works 87, 151 

AX, use of 44 



BALKS, bay, etc., defined... 284-285 
BALLAST, for R. R., object of 377 
BANK, GUN, definition of, 
relative advantages of, 

and embrasures 70 

dimensions of, where 

placed 102 

space required for 100 

BARREL, buoyancy of, how 

determined 325 

BARRELS, closed, piers of, 

construction of 330 

open, piers of, construc- 
tion of 328 

open, safe load of 329 



Par. 
BARRICADE, use and con- 
struction of 61 

for doors of buildings 195 

BATTERIES, telegraph, how 

carried 418 

B \Y, length of, how found. . . 317 

BEDS, camp 499 

liERM, definition of, etc 65, 99 

advantages and disadvan- 
tages of 78 

RINDING, fascines 117 

BISECTING an angle, method 

of 20 

BLOCKS, description of, etc , 

running.. 228 

BLOCKHOUSE, use and con- 
struction of 144 

Spanish.. 145a 

in isolated places 145 

BOAT, buoyancy of, how 

found 316 

BOX or barrel to sling 223 

ponton, construction of .. . 323 

BRACKETS, telegraph 410 

BREAKING loads of ropes ... 218 
BREAKS in telegraph lines. . 419 
BRIDGE, anchored to haw- 
ser 343 

beams, of iron, how de- 
stroyed 446 

connection of with shore, 

how made 350 

computing strength of.. . 255 

double lock 275 

expedients 278 

floating, description of, 

modification of 306 

floating, improvised 352a 

flying, description of 3u9 

forming, b y s u c cessive 

pontons 346 

forming, by parts 347 

forming, by rafts 348 

forming, by conversion . . 349 
masonry, how destroyed. . 

440-441 

maximum load for 247 

name of, how derived. . .248, 310 

Paine's 260 

pile 269 



222 



Index. 



Par. 
BRIDGE— Continued. 

protection of, from float- 
ing objects 352 

railroad, repair of 407 

requirements of 244 

short, how anchored 343 

single lock 274 

single sling 276 

spar xaiiroad 245 

suspension 280-6 

suspension, how destroyed 450 

swing 351 

trail 308 

treble sling 277 

twenty-five feet or less 258-9 

twenty-five feet or over. . 

261,271,276 

BROADSIDE VILLAGE, how 

defended 211 

BiiUSH huts 503 

sentry boxes 504 

B RUS H WOO D, bund les of, va- 
rieties and sizes 115 

late and method of clear- 
ing 46 

roads 371 

BUILDING, defense of , how 
regarded, first line, how 

far distant 191 

doors of, how barricaded, 195 

flank defense of 199 

how used for defense 189 

loopholingof 194 

materials used in defense 

of 200 

precautions in defense of. 19* 

removal of 43, 438 

requisite of, for defense . . 190 
steps in preparing for de- 
fense 193 

windows -of, how barri- 
caded 197 

BUO Y ANO Y of casks, how de- 
termined 325 

BUZZACOTT oven, descrip- 
tion of 497 

CABLE, charge of explosive 

to cut 450 

swinging, length of 309 

CAMPBEDS 499 

CAMPS, drainage 498 

dry and healthy sites 

for 457,459 

selection of 455, 456, 462 

unhealthy sites for 458, 460 

windbreaks for 500 

CANISTER, description of... 11 

CANVAS PONTON, U. S 319 

OANV AS RAFT, descnpt ion of 303 
CAPITAL of field works ... 82 
CAPONIERS, objections to, 85, 146 

stockade work used for 188 

used in flanking buildings, 199 

CAPSTAN, description of 242 

improvised field 243a 



Par. 
CASE MATES, use and general 

form of 138 

how constructed, floor 

space in 139 

CENTRIFUGAL FORCE of 

train 383 

CHARCOAL, uses of 481 

how made 482 

CHARGES, several exploded 

at same time 435 

CHESS described. 248 

CHEVAUX-DEFRISE 56 

CHOKER FASCINE, descrip- 
tion and use of 117 

CIRCULAR VILLAGE, how 

defended 214 

CLARIFICATION of water . . 476 

CLAY ROADS 367 

COMMAND OF WORKS, defi- 
nition of 71 

COMMON TRENCH work, how 

made, uses of 156 

COMMUNICATIONS, c o n - 

struction of 373,374 

in woods 177 

CONCENTRATED LOAD on 

bridge 253 

CONDUCTOR, metallic, for 

telegraph .*.... 408 

CONNECTING WIRES, how 

done 431 

CORDUROY ROADS 370 

COUNTER-SCARP, definition, 

etc 65, 79 

galleries 85 

COVERforguns 40a 

in woods, how obtained ... 176 

CRAB 240 

CREST, exterior 67 

interior 66 

military 153 

CRIB piers, construction of.. 268 

ponton, construction of... 322 

CROSS, in telegraph wires 419 

CROSS ARMS, telegraph 410 

CROSSING of rivers, selec- 
tion of, how determined, 289 

C ROSSINGS. railroad 385 

CROW'S FEET 56 

CUTTING, how defended. . .171, 172 



DEAD LOAD on bridges 253 

DEBRIS, removal of 48 

DEFENDERS of woods, num- 
ber of 179 

DEFENSE, of fences 168 

passive, with respect to 

lines of works 149 

DEFILADE, definition of.... 88 

in plan 89 

in section 90,91 

with two planes 92 

DEPTH of fords 29o 

DERRICK, description of.... 237 

in using 240 



Index. 



223 



Par. 
DESTROYING railroads, by 

whom done 399 400 

bv whom ordered 401 

nf telegraph lines 420 

DETONATOK 429 

with fuse 428 

electrical 429 

DIGGING wells 470,471, 472 

DIMENSIONS of loopholes ... 16*4 

DISABLING railroads 398 

DISTANCE between two in- 
accessible point s,method 

of finding 24 

DISTRIBUTED load 253 

DITCH 65,81, 361 

depth of 96 

method of digging..., Id 

DOORS, how barricaded 105 

DOU BLE lock bridge 275 

DRAINS, catch and covered. . SGI 

DRAINAGE of camps 498 

of roads 361 

DRINKING water 465-9 

DRIVEN wells 47.-5-4 

DRIVING piles 270 

DYNAMITE, use of with de- 
tonator 428 



EARTH, excess of at salients. 97 
in embankments, space 

occupied by 96 

roads 306 

EARTHWORKS, calculation 

of dimensions of 95 

ELECTRICAL fuse 423 

EMBANKMENT, how defend- 
ed 170 

EMBARKATION, in ferrying 301 

EMBRASURE 69 

used when, details and 

construction of 103 

space required for 100 

ENGINE, locomotive 389 

ENGINEERING, Military, 

Field, definition of l 

EPAULEMENT, gun 40a, 70 

relative advantage of, and 

embrasures 70 

EQUILATERAL TRIANGLE, 

method of laying out 21 

ESCAPE in telegraph lines... 419 

ESCARP 65, 79 

EXPEDIENTS, bridge 278 

EXPLODER, electrical 430 

EXPLOSIVES, kind general- 

ly used 421 

tab e of comparative 

strength of 453 

EXTENDING along zig-zag.. 155 

working party K>9, 110, 155 

EXTENSION on flying sap, 

method of 158 

EYE-BARS, how cut 448 

EYE-SPLICE, to make 222 



Par. 

FACES of works 82 

FARMS, principles of defense 

applied to 203 

FASCINES, size, weight, and 

making of 117 

FASTENINGS, rail 382 

FAULTS in telegraph lines. 410-20 

FENCES, defense of 168 

removal of when 48 

FERRY, the rope 307 

FERRY T ING by boat, embark- 
ation, and unloading 301 

by raft 302 

FIELD GUN 8, destruction of 451 

range of. 13 

FIELD LEVEL,descripfron of 26 

FILTERS, portable 483-4 

simple 485 

FILTERING water 480-1 

FIRE, as regards direction, 

trajectory 8 

double tier of, for walls. . . 167 

sector of, discussion of 86 

working parties exposed 

to Ill 

FLANK defense of buildings 199 

FLANKS of works 82 

FLOOR space in casemates. . . 139 
FLOATING piers, essentials 

of 314 

FLYING BRIDGES, raft for. . 340 

telegraph lines 418 

sap, description of 157 

sap. method of extension 

along 158 

FORDS, how made impassa- 
ble 58 

with sandy bottom 291 

depth of , requisite of 290 

in mountainous country. . 291 

level country 291 

how marked, position of, 

how determined 293 

precautions in selecting. . 295 

re-examinations of 296 

where found 292 

FOREGROUND, extent of 

clearing 43 

FORM, strap iron gabion 120 

wicker gabion 118- 

of roads 359 

FORMING BRIDGE by con- 
version 349 

by parts 347" 

by rafts 348- 

bv successive pontons ... 346 

FORTS, how distinguished. .. 84 
FORT WAGNER, parallels 

and approaches to 160 

FORTIFICATION, classes of. 2 
compared to other milita- 
ry expedients 7 

object of 

subdivision of field 3 

FOUGASSE, construct ion, use 

and charge for 59 



224 



Index. 



Par. 
FRAISES, construction and 

use of 55 

FROGS 384 

railroad, how destroyed. . 444 

FUSE 427 

how used . . 428 



GABIONS, hoop or strap iron, 

weight and making of.. . 120 

method of carrying 157 

sheet iron, making of 121 

wicker, size, weight, and 

making of 118 

making of without a gabi- 
on form 119 

GATES, destruction of 437 

GIN, description of 239 

using 240 

lashing, making of. 227 

GLACIS 63,80 

GORGE of works 82 

GRADIENT, limiting of roads 355 

GRAIN, removal of standing. 47 

GRASS, removal of standing. 47 

G R WEL ROADS 368 

GRILLAGE 493 

GAUGE of railroads 380 

GUARDING water supply... 464 

GUN-COTTON 422 

how detonated 428 

GUN E PAUL E ME NTS and 

pits 40 i 

GUNPOWDER, how ignited. 428 

used as an explosive 424 

GUTTERS 361 

HARD WATER 477 

HASTY DEMOLITION, ta- 
bles showing charges 

for 452 

HE AD LOGS, use of 40 

HEALTHY CAMPS .457, 459 

HEDGES, advantages of . how 

derived, principles of .. . 169 

removed, when 48 

HEIGHTS over which fire 

mav be delivered 13 

HITCH ES, knots, etc 219 

HOLDFASTS, description of. . 243 
HOOPS, making of, for strap 

iron gabions 120 

HO RS E, power of on grades . . 356 

HOUSES, demolition of 438 

HURDLES, continuous, con- 
struction of 123 

size, weight and making of 122 

HUTS, brush. 503 

how made, etc 501 

Armj' of Potomac (Major 

Smart's) 502 

allowance of space in. 501 

bamboo 505 



Par. 

ICE 297 

thickness of, how in- 

c eased 299 

thickness of for various 

loads. 298 

INFANTRY APPROACHES 

in siege operations. . 154 

INTERVALS between trench- 
es 36 

method of taking,by work- 
ing parties 100 

usual for working par- 
ties Ill, J12 

INSULATORS, telegraph 412 

INSULATED WIRE JOINTS 431 
INTRENCHMENTS, HASTY, 
advantages and disad- 
vantages of 39 

concealment of 38 

conditions to be fulfilled 

by 28 

consist of 28 

for men standing 3L 

for skirmishers lying 28 

for two ranks kneeling... 30 

for supports and reserves. 33 

intervals in line of 36 

isolated- 32 

location of depends upon. 35 

on slopes 34 

Spanish 31 

IRON PLATES, how cut 445 

ISOLATED PITS S2 

JOINTS for telegraph wire. . . 417 

American twist 417 

insulation of 431 

rail 381 

JUNCTIONS, railroad 386 

KING-POST TRUSS 272 

KITCHENS 491-2 

covered 494 

KNOTS, hitches, etc 219 



LANCES, military/telegraph. 418 

LASHINGS, gin 227 

rack 224 

shear 226 

transom 225 

LATRINES 487, 490 

LEAKS in telegraph line 419 

LEVEL, field, description of. 26 

uses of 27 

LINES, cutting of ditch and 

trench 101 

LINE, first, falling back past 

houses 192 

parallel to given line, 

method of constructing. 23 
LINES, second and third in 

woods 168 



Index. 



Par. 
LOAD, distributed ,dead. and 

moving 253 

LOADING HORSES in rail- 
road cars 393, 394 

LOADING WAGONS on rail- 
road cars 396 

LOG, cubic contents of 254, 335 

buoy a ncy of 334 

LOGS, pi rs of, construction 

of 338 

LONG SPLICE, to nmke '221 

LOOPHOLES, dimensions of 164 
height of, how influenced. 166 

how made 40 

in buildings 194 

LO>PHOLING WALLS 163 

method of 164, 165 



MACADAM ROADS 364 

MACHICOULIS gallery, con- 
struction of, use of 199 

MAGAZINE, general plan 

of 141, 142 

large, small in parapet. ... 140 

of gabions and fascines. . . 143 
rifle, range, speed, and 

tire of 14 

MAGNETO EXPLODE* 430 

MARKING FORDS 293 

MATEKIALS for bridges. ... 287 

for road covering* 365 

revetting 114 

used in defense of build- 
ings 200 

MAXIMUM LOAD for bridge 247 
MERLON, deilnition of, rule 

as to minimum length of 104 

METAL TIES 379 

MILITARY ENGINEERS,du- 

ties of 421 

MILI I'ARY TELEGRAPH 

lines 418 

MINES, land, quantity of ex- 
plosive necessary 60 

MOVING or LIVE LOADS. ... 253 



OBJECTS, floating, protec- 
tion of bridge from 352 

OBSTACLES, conditions gov- 
erning use of 49 

OFFICE TELEGRAPH.tieat- 

ment of when captured . 420 

OVENS 495-6 

Buzzacott... 497 

ORGANIZATIONS, or parts 
of, used as working par- 
ties 42 

OVERHAUL TACKLE 231 



PAINE'S BRIDGE 260 

PALISADES, consist of 51 

PALISADING, destruction of 435 

PAIRING 118 



225 

Pai 

. 10L 



PAN COUPE 

PARADOS, definition of... 
method of determining 

height of.... 93 

PARALLEL to a given line, 

method of constructing. 23 
PARALLELS and approaches, 

Fort Wagner 160 

PARAPET 63, 67, 81 

PERPENDICULAR to a line 

method of erecting 19 

PICKETS, forked 119 

gabion lis 

PIERS, bridge, how de- 
stroyed 440, 449 

floating, essentials of 314 

of casks, precautions in 

using 327 

of open boats, precautions 

in using 315 

of open cask-, construc- 
tion of 328 

of closed casks, construe 

tionof 330,333 

of logs, construction of .338, 339 

PILE BRIDGES 269 

driving 2^9 

PLANK ROADS 372 

PLANKS, when used for re- 
vetments 124 

PLOWS, useof 33 

PONTON CANVAS, U. S 319 

crib, construction of 322 

PONT<»N, box, construction 

of 

reserve train, U. S 

wagon body, construction 

of 

P<>LES, telegraph, how num- 
bered 

telegraph, how guyed, 
number to mile,prepaia- 
tion of, protection from 
lightning, raising of, 

size of, where run 409,411 

PORTABLE RAMP 393 

Alters 483, 484 

truss 279 

POSITION, defensive, defini- 
tion of, chief requisite 

of 4 

choice of 42 

strength of 153 

conditions to be fulfilled.. 4 

of ford, how determined.. 293 

POWER of horse on slopes.. . 356 

exerted by man 236 

of tackle 233-5 

PRECAUTIONS, additional, 

in defending buildings.. 198 

in fording 295 

PROFJ LES, angle, how deter- 
mined 94 

definition and nomencla- 
ture of 65 

normal, of field works 99 



323 

320 



324 
415 



226 



PROFILING, method of. 
PULLEY, description of. 



Index, 



Par, 

. 94 
. 228 



QUEEN-POST TRUSS 273 

RACK, fascine, description 

and use of 117 

lashing to make 224 

RAFT, canvas, description of, 303 

for trail bridge 308 

of skins 304 

RAFTS, advantages and dis- 
advantages of 305 

for flying bridge 340 

swinging, for iraffic 351 

RAIL FASTENINGS 382 

form of 380 

joints 381 

how cut 435 

straightening 407 

RAILROAD, bridge 245 

crossings 385 

junction 386 

wye 387 

turntable 388 

RAILROADS, duties of troops 

in connection with 375 

description of 377 

destroying and disabling, 

by whom done 398-400 

how disabled and des- 
troyed 402, 403 

repair of 404 

rolling stock, buildings, 

etc 390, 391 

RAMP, portable 393 

Major Fechet's 397 

semi-permanent 395 

simple form of 392 

RANDING 122 

REDOUBTS r 84 

RELIEFS, 1st, 2nd and 3rd of 
working party, cutting 

lines for tasks of 101 

of field work, definition of 72 

RESERVE TRAIN, ponton, 

U S 320 

RE VE TMENT\ " definition' of 113 
making and qualities of 

adobe 137 

of brushwood 128 

of fascines 129 

of gabion 130 

of hurdle and continuous 

hurdle 131 

of pisa 136 

of plank 124, 132 

of posts 135 

of sand bag 133 

of sod 126, 133 

of timber 125, 132 

of bamboo 137a 

RIBB\VDS 55 

ROAD-BED 360 

defense of 173 

materials 365 



Par. 

ROADS, brushwood 371 

clay 367 

corduroy 370 

desirable conditions in 354 

drainage of , 361 

ean h 366 

form of 359 

gravel 368 

knowledge of 353 

limiting gradients of 355 

plank 372 

repair of 369 

surface of 362 

width of 358 

ROAD W AY, weight of, steadi* 

ness of. 313 
width of on bridges. '.'. 248, 280-6 

ROPE, breaking loads of, 

weight of 218 

composition, size of, etc . . . 216 

tlOPE, parts of 219, 230 

rule for strength of 217 

expedient for tightening, 308 

ROUND TIMBER, strength of, 255 

RUNNING BLOCKS 228 



SAG in telegraph wire 

SALIENT village, how de- 
fended 

SAND-BAGS, materials, size, 

capacity, and filling 

SAP, flying, description of.. 

SAW, teeth of 

use of 

SECTOR OF FIRE, definition 
of andapp ication to dif- 
ferent traces 

SELECTING CAMPS 455-6, 

SENTRY BOXES 

SEWING, method of, for gabi- 
ons and hurdles 

SHEAR LASHINGS 

SHEARS, description of 

method of using 

SHELL 

charges, how exploded 

penetration 

shrapnel 

SHORT SPLICE, to make 

SHOVEL ERS, extra, piovid- 

ed when 

SIDINGS, railroad 

SINGLE LOCK BRIDGE 

SINGLE SLING BRIDGE.. 
SITE for floating bridge, selec- 
tion of 

plane of, definition 

SIZE OF TELEGRAPH 

WIRE 

SLEWING 

SLOPE, banquette 

description of 

exterior 65 

interior 65 

superior t5 



414 

212 

127 

157 

44 

44 



86 
462 
504 

118 

226 

238 

240 

9 

12 
15i 

10 
220 

101 
384 
274 
276 

311 
73 

408 

122 

65 

17 

, 77 
, 75 
■ 76 



I?idex. 



227 



Par. 

SMALL PITS, how made 57 

how dest royed. 453 

SNATCH BLOCK 228 

SODS for revetments, cutting 

*o* and laying 126 

SPAN, superstructure, string- 
ers or balks, side rails, 

etc 248 

SPANS, 25-ft. or less 258. 259 

25-ft. or over 261, 271, 276 

SPARS, arrangement of 257 

SPLICE, long 221 

eye 222 

SPLINTER-PROOF for tren- 
ches 35 

STOCKADE, advantages of, 

definition of 180 

how destroyed 436 

kind of timber preferable 

for 186 

loopholes in 184 

loopholes, when cut in 185 

of vertical timbers 182 

of same, square and round 

timbers 183 

of horizontal timber 187 

STOCKADE, of K. R. iron, de- 
stroyed how 436 

when employed 181 

work used for tambours 

and caponiers 188 

STRAIGHTENING KAILS. . . 407 
STREAMS, unfordable, how 

passed 294 

velocitv of, how deter- 
mined 296 

width of, how determined, 312 

STRENGTH OF MATERIALS 249 

of rope 217, 218 

SLB-DRAINS 361 

SUSPENSION BRIDGES 280-6 

S^YITCH, split and stub 384 

TABLE of breaking loads ... 218 

of constant "O" 253 

of weights of materials 256 

showing amounts of revet- 
ting materials for 100 

linear feet of revetment, 137 

TACKLE, description of 229 

formula for power of 235 

powerof 233-4 

to prevent twisting 232 

to round in, to overhaul. . . 231 

TAMBOUR 147 

stockade work used for. . . 188 

used in flanking buildings, 199 

TASKS (PL 14, 16) 111, 112 

laying out of 101 

in constructing parallels 

and approaches PI. 22 

responsibility for comple- 
tion of 106 

TELEGRAPH MESSAGES. .. 408 

lines, how destroyed 420 

TELEPHONE, outpost cart for 418 



Par. 

TELFORD ROADS 363 

TERREPLEIN 74 

THICKNESS of materials 

proof again st small arms, 15 

TIES, metal 379 

wood 378 

TIMBER BRIDGE, how de- 
stroyed 433 

felled, removal of 45 

kinds preferable for stock- 
ade 186 

round for revetments 125 

standing, removal of 43, 44 

TOOLS, carrying of by work- 
ing parties 108 

cutting, intrenching used 

in the field 41 

taking of, by working par- 
ties . . 107 

used in felling tember 44 

TORPEDO, U.S. bridge 433 

TORPEDOES, automatic 453 

TRACE, definition of 64 

selection of 89 

TRANSOM, strength of 250 

TRAVERSE, definition of 68 

method of determining 

height of 93 

TREAD BANQUETTE 65 

TREBLE SLING BRIDGE.... 277 

TREE INSULATOR and tie.. 415 

TREES, cutting of 44,45 

how to fell with explosives. 432 

TRKNCH 65 

common .uses of, how mt.de, 156 

drainage of. 98 

method of digging 101 

TRENCHES, advantages and 

disadvantages of 39 

conditions to be fulfilled 

by 28 

disguising location of 38 

intervals in line of 36 

kneeling or sitting 30 

location of 35 

lying 29 

standing bl 

Spanish 31 

TROOPS, weight of on bridge, 252 

TRESTLES, capped 264 

tie block 263 

two-legged 265 

three-legged 266 

four-legged 267 

six-legged 262 

TRUSS, king- post 272 

queen-post 273 

portable 279 

TUNNELS, how destroyed.... 442 

repair of 406 

TURNTABLES, railroad 388 

UNLOADING in ferrying. ... 301 

horses from R. R. cars.. 393, 394 

wagons from cars 396 

URINALS 488, 489 



228 Index. 

Par. 
VELOCITY of streams, how 

determined 296 

VILLAGE, advantages and 
disadvantages of for de- 
fense 206 

artillery, where placed in 

defence of 215 

broadside, how defended.. 213 

circular, how defended 214 

cover for supports and re- 
serves in 215 

in defense of, precautions 

necessary 205 

defense of depends on.. .. 208 
arrangements for defense 

of 205 

garrison of, how deter- 
mined 211 

objects in holding 207 

salient, how defended 212 

value of, for defense 205 

arrangement for defense 
of, how made 210 



WAGON BODY PONTON, con- 
struction of 324 

WAGONS, prepared for cross- 
ing on ice. -, 299 

WALLS, for double tiers of 

fire 167 

discussion of as military 

expedients 161 

loopholing 163 5 

preparation of for defense 162 

removal of 48 

how destroyed 439 

WATER, clarification of 476 

drinking 465-9 

filtering 480-1 

guarding 464 

necessity of" and amount 

required 463-4 

WATER TABLES on roads... 361 

WATLING 118 

WEEDS, removal of 47 

WEIGHT of materials 256 

of rope 218 

of troops on bridge 252 

WELLS, digging of 470-2 

rt riven 473-4 

WIDTH OF ROADS 358 

WINCH 240 

WINDLASS, description of.. 241 
WINDBREAKS, for damps.... 500 
WINDOWS of buildings, how 

barricaded 197 



Par. 

WIRE, connection of 431 

entanglements, high, low, 

how made 52, 53 

entanglements, how de- 
stroyed 454 

how stretched, hanging 

of , secured to 414 

h w strung across roads.. . 411 
how strung across streams 415 

telegraph 408 

tie 413 

WITHES, making and use of 117 

WOODS artillery in. 179 

communications in 177 

cover in 176 

lying beyond position 175 

number of defenders of ... 179 
preparation of ed^e of . . . 174 

2d and 3d lines in 178 

WORKS, constructed by 

troops to occupy 5 

double line of 150 

fixed types of necessary. . . 6 
groups of, intermediate, 

when used 149 

line of f. 148 

advantages and principles 

of 149 

WORKS, field, conditions to 

be fulfilled 62 

calculation of cross sec- 
tion of 95 

classification as to trace.. 83 

defilade of 88. 89, 90, 91, 92 

details of construction of 

99,110,101 

length of crest for as- 
sumed girrison 100 

open, closed, and half 
closed, definitions, ad- 
vnntages, and disadvan- 
tages 83 

continuous line of, crem- 
aillere, blunted redan, 
redan with curtains, te- 
naille. tenaille and re- 
dan, trace of 152 

WORKING parties, extension 

of 109, 110 

organization of 105 

when under fire Ill 

WYE, R. R 387 

ZIG-ZAG, direction of, length 

of 159 

extending along : 155 



Organization and Tactics. 

(second edition.) 

. . BY . . 

LIEUT.-COLONEL ARTHUR L. WAGNE&V 

Vssistant Adjutant-General U. S. Army ; formerly Instructor in the Art of 
War at the U. S. Infantry and Cavalry School, 



CONTENTS. 



Introduction.— Organization and Discipline. — Characteristics 
of the Three Arms. — Historical Sketch of Modern Infantry. — 
Infantry in Attack and Defense. — Historical Sketch of Modern 
Cavalry. — Cavalry in Attack and Defense. — Historical Sketch oi 
Field Artillery. — Artillery in Attack and Defense.— The Three 
Arms Combined. — Convoys. 



THIS BOOK has been officially adopted by the War Department as a 
standard in the examination of officers of the Regular Army for promo- 
tion. It has also been officially adopted as a text-book in 

The U. S. ARTILLERY SCHOOL, Fort Monroe 
The U. S. INFANTRY and CAVALRY SCHOOL, Fort Leav- 
enworth. 

The U. S. CAVALRY and LIGHT ARTILLERY SCHOOL, Fort 

Riley. 
The U. S. ENGINEER SCHOOL, Willets Point, N. Y. 



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THE SERVICE 

. . OF . . 

Security and Information. 

REVISED EDITION (FOURTH). 

By Lieut. -Colonel Arthur L. Wagner, 

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CONTENTS. 



Chapter I. — Introduction. Chapter VJI — Spies. 

Chapter II. — Advance Guards. Chapter VIII — Orientation and 

Chapter J II. — Outposts. Map-Reading. 

Chapter IV. — Reconnaissance. Chapter IX.— Indian Scouting. 

Chapter V. — The Cavalry Appendix I. — Advance Guard 

Screen. Drill. 

Chapter VI. — Rear Guards. Appendix II. — Questions for 

General Review. 

Illustrated with Fifteen Plates, 



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The U. S. ENGINEER SCHOOL, Willets Point, N. Y. 



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Roosevelt, 1st U. S. Volunteer Cavalry (Rough Riders). 300 
pages, cloth, octavo, $1.50. 

Address HUDSON-KIMBERLY PUBLISHING CO., 
1014 Wyandotte St., Kansas City, Mo. 



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